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LI  BR  ARV 


UNIVERSITY   OF   CALIFORNIA. 

GIK'T    OK" 
BIOLOGY 


Received 
Accessions  No. 


Shelf  No. 


INTRODUCTION  AND  SUCCESSION 


VERTEBRATE  LIFE  IN  AMERICA. 


AIST    ADDRESS 


DELIVERED   BEFORE   THE 

AMERICAN    ASSOCIATION    FOR   THE    ADVANCEMENT   OF    SCIENCE, 
AT    NASHVILLE,    TENN.,    AUGUST    30,    1877, 


PROFESSOR   0.    C.    MARSH, 

i< 

Vice  President. 


L I  B  R  A  R  Y 
UKIVEBSiTY  OF 
.CALIFORNIA. 


Tuttle,  Morenoase  A  Tuylor,  Printers,  New  f-Uven,  Conn. 


LIBRARY 

UNIVERSITY  OF 

CALIFORNIA. 


INTRODUCTION  AND  SUCCESSION  OF  VERTEBRATE 
LIFE  IN  AMERICA. 


THE  origin  of  life,  and  the  order  of  succession  in  which  its 
various  forms  have  appeared  upon  the  earth,  offer  to  science 
its  most  inviting  and  most  difficult  field  of  research. 
Although  the  primal  origin  of  life  is  unknown,  and  may  per- 
haps never  be  kno.wn,  yet  no  one  has  a  right  to  say  how  much 
of  the  mystery  now  surrounding  it  science  cannot  remove. 
It  is  certainly  within  the  domain  of  science  to  determine  when 
the  earth  was  first  fitted  to  receive  life,  and  in  what  form  the 
earliest  life  began.  To  trace  that  life  in  its  manifold  changes 
through  past  ages  to  the  present  is  a  more  difficult  task,  but 
one  from  which  modern  science  does  not  shrink.  In  this  wide 
field,  every  earnest  effort  will  meet  some  degree  of  success ; 
every  year  will  add  new  and  important  facts ;  and  every 
generation  will  bring  to  light  some  law,  in  accordance  with 
which  ancient  life  has  been  changed  into  life  as  we  see  it 
around  us  to-day.  That  such  a  development  has  taken  place, 
no  one  will  doubt  who  has  carefully  traced  any  single  group 
of  animals  through  its  past  history,  as  recorded  in  the  crust  of 
the  earth.  The  evidence  will  be  especially  conclusive,  if  the 
group  selected  belongs  to  the  higher  forms  of  life,  which  are 
sensitive  to  every  change  in  their  surroundings.  But  I  am  sure 
I  need  offer  here  no  argument  for  evolution ;  since  to  doubt 
evolution  to-day  is  to  doubt  science,  and  science  is  only  another 
name  for  truth. 


Taking,  then,  evolution  as  a  key  to  the  mysteries  of  past  life 
on  the  earth,  I  invite  your  attention  to  the  subject  I  have 
chosen :  THE  INTRODUCTION  AND  SUCCESSION  OF  VERTEBRATE 
LIFE  IN  AMERICA. 

In  the  brief  hour  allotted  to  me,  I  could  hardly  hope  to  give 
more  than  a  very  incomplete  sketch  of  what  is  now  known  on 
this  subject.  I  shall,  therefore,  pass  rapidly  over  the  lower 
groups,  and  speak  more  particularly  of  the  higher  vertebrates, 
which  have  an  especial  interest  to  us  all,  in  so  far  as  they 
approach  man  in  structure,  and  thus  indicate  his  probable 
origin.  These  higher  vertebrates,  moreover,  are  most  important 
witnesses  of  the  past,  since  their  superior  organization  made 
them  ready  victims  to  slight  climatic  changes,  which  would 
otherwise  have  remained  unrecorded. 

In  considering  the  ancient  life  of  America,  it  is  important  to 
bear  in  mind  that  I  can  only  offer  you  a  brief  record  of  a  few 
of  the  countless  forms  that  once  occupied  this  continent.  The 
review  I  can  bring  before  you  will  not  be  like  that  of  a  great 
army,  when  regiment  after  regiment  with  full  ranks  moves  by 
in  orderly  succession,  until  the  entire  host  has  passed.  My 
review  must  be  more  like  the  roll-call  after  a  battle,  when  only 
a  few  scarred  and  crippled  veterans  remain  to  answer  to  their 
names.  Or  rather,  it  must  resemble  an  array  of  relics,  dug 
from  the  field  of  some  old  Trojan  combat,  long  after  the  con- 
test, when  no  survivor  remains  to  tell  the  tale  of  the  strife. 
From  such  an  ancient  battle-field,  a  Schliernann  might  unearth 
together  the  bronze  shield,  lance-head,  and  gilded  helmet  of  a 
prehistoric  leader,  and  learn  from  them  with  certainty  his  race 
and  rank.  Perhaps  the  skull  might  still  retain  the  barbaric 
stone  weapon  by  which  his  northern  foe  had  slain  him.  Near 
by,  the  explorer  might  bring  to  light  the  commingled  coat  of 
mail  and  trappings  of  a  horse  and  rider,  so  strangely  different 
from  the  equipment  of  the  chief,  as  to  suggest  a  foreign  ally. 
From  these,  and  from  the  more  common  implements  of  war 
that  fill  the  soil,  the  antiquary  could  determine,  by  patient 
study,  what  nations  fought,  and,  perhaps,  when,  and  why. 


By  this  same  method  of  research,  the  more  ancient  strata 
of  the  earth  have  been  explored,  and,  in  our  Western  wilds, 
veritable  battle-fields,  strown  with  the  fossil  skeletons  of  the 
slain,  and  guarded  faithfully  by  savage  superstition,  have  been 
despoiled,  yielding  to  science  treasures  more  rare  than  bronze 
or  gold.  Without  such  spoils,  from  many  fields,  I  could  not 
have  chosen  the  present  theme  for  my  address  to-night. 

According  to  present  knowledge,  no  vertebrate  life  is  known 
to  have  existed  on  this  continent  in  the  Archaean,  Cambrian,  or 
Silurian  periods;  yet  during  this  time,  more  than  half  of  the 
thickness  of  American  stratified  rocks  was  deposited.  It  by 
no  means  follows  that  vertebrate  animals  of  some  kind  did  not 
exist  here  in  those  remote  ages.  Fishes  are  known  from  the 
Upper  Silurian  of  Europe,  and  there  is  every  probability  that 
they  will  yet  be  discovered  in  our  strata  of  the  same  age,  if  not 
at  a  still  lower  horizon. 

In  the  shore  deposits  of  the  early  Devonian  sea,  known  as 
the  Schoharie  Grit,  characteristic  remains  of  Fishes  were  pre- 
served, and  in  the  deeper  sea  that  followed,  in  which  the 
Corniferous  limestone  was  laid  down,  this  class  was  well 
represented.  During  the  remainder  of  the  Devonian,  Fishes 
continue  abundant  in  the  shallower  seas,  and,  so  far  as  now 
known,  were  the  only  type  of  vertebrate  life.  These  fishes 
were  mainly  Ganoids,  a  group,  represented  in  our  present 
waters  by  the  Gar-pike  (Lepidosleus)  and  Sturgeon  (Acipenser), 
but,  in  the  Devonian  sea,  chiefly  by  the  Placoderms,  the  exact 
affinities  of  which  are  somewhat  in  doubt.  With  these  were 
Elasmobranchs,  or  the  Shark  tribe,  and  among  them  a  few 
Chimaeroids,  a  peculiar  type,  of  which  one  or  two  members  still 
survive.  The  Placoderms  were  the  monarchs  of  the  ocean.  All 
were  well  protected  by  a  massive  coat  of  armor,  and  some  of 
them  attained  huge  dimensions.  The  American  Devonian  fishes 
now  known  are  not  as  numerous  as  those  of  Europe,  but  they 
were  larger  in  size,  and  mostly  inhabitants  of  the  open  sea. 
Some  twenty  genera  and  forty  species  have  been  described. 


6 

The  more  important  genera  of  Placoderms  are,  Diniclithys, 
Aspidichthys,  and  Diploynathus,  our  largest  Palaeozoic  fishes. 
Others  are,  Acanthaspis,  Acantholepis,  Coccosteus,  Macropetalich- 
thys,  and  Onychodus.  Among  the  Elasmobranchs  were,  Clado- 
dus,  Ctenacanthus,  Machcer acanthus,  Rhynchodus,  and  Ptyctodus, 
the  last  two  being  regarded  as  Chima3roids.  In  the  Chemung 
epoch,  the  great  Dipterian  family  was  introduced  with  Dipterus, 
Heliodus,  and  possibly  Ceratodus.  Species  of  the  European 
genera,  BothrioUpis  and  Holoptychius,  have  likewise  been  found 
in  our  Devonian  deposits. 

With  the  close  of  the  Devonian,  came  the  almost  total  extinc- 
tion of  the  great  group  of  Placoderms,  while  the  Elasmobranchs, 
which  had  hitherto  occupied  a  subordinate  position,  increase  in 
numbers  and  size,  and  appear  to  be  represented  by  Sharks, 
Eays,  and  Chimseras.  Among  the  members  of  this  group  from 
the  Carboniferous,  were  numerous  Cestracionts,  species  of 
Cochliodus  of  large  size,  with  others  of  the  genera  Deltodus, 
Helodus,  Psammodus  and  Sandalodus.  Of  the  Petalodonts, 
there  were  Antliodus,  Chomatodus,  Ctenoptychius,  Petalodus  and 
Petalorhyrtckus ;  and  of  the  Hybodonts,  the  genera  Cladodus, 
Carcharopsis  and  Diplodus.  These  Elasmobranchs  were  •  the 
rulers  of  the  Carboniferous  open  sea,  and  more  than  one  hun- 
dred species  have  been  found  in  the  lower  part  of  this  forma- 
tion alone.  The  Ganoids,  although  still  abundant,  were  of 
smaller  size,  and  denizens  of  the  more  shallow  and  confined 
waters.  The  latter  group  of  fishes  was  represented  by  true 
Lepidostidae,  of  the  genera  Palceoniscus,  Amblypterus,  Platyso- 
mus  and  Eurylepis.  Other  genera  are,  Rhizodus,  Megalichthys, 
Ctenodus,  JEdestus,  Orodus,  Cten acanthus,  Gyracanthus,  and  C<xla- 
canthus.  Most  of  these  genera  occur  also  in  Europe. 

From  the  Permian  rocks  of  America,  no  vertebrate  remains 
are  known,  although  in  the  same  formation  of  Europe  Ganoids 
are  abundant;  and  with  them  are  remains  of  Sharks,  and  some 
other  fishes,  the  affinities  of  which  are  doubtful.  The  Palaeo- 
zoic fishes  at  present  known  from  this  country  are  quite  as 
numerous  as  those  found  in  Europe. 


In  the  Mesozoic  age,  the  Fishes  of  America  begin  to  show  a 
decided  approach  to  those  of  our  present  waters.  From  the 
Triassic  rocks,  Ganoids  only  are  known,  and  they  are  all  more 
or  less  closely  related  to  the  modern  Gar-pike,  or  Lepidosteus. 
They  are  of  small  size,  and  the  number  of  individuals 
preserved  is  very  large.  The  characteristic  genera  are,  Catop- 
lerus,  Ischypterus,  Ptycholepis,  Rhabdolepis,  and  Turseodus. 
From  the  Jurassic  deposits,  no  remains  of  fishes  are  known, 
but  in  the  Cretaceous,  ichthyic  life  assumed  many  and 
various  forms ;  and  the  first  representatives  of  the  Teleosts, 
or  bony  fishes,  the  characteristic  fishes  of  to-day,  make 
their  appearance.  In  the  deep  open  sea  of  this  age,  Elas- 
mobranchs  were  the  prevailing  forms,  Sharks  and  Chimseroids 
being  most  numerous.  In  the  great  inland  Cretaceous  sea  of 
North  America,  true  osseous  fishes  were  most  abundant,  and 
among  them  were  some  of  carnivorous  habits,  and  immense 
size.  The  more  sheltered  bays  and  rivers  were  shared  by  the 
Ganoids  and  Teleosts,  as  their  remains  testify.  The  more 
common  genera  of  Cretaceous  Elasmobranchs  were,  Otodus, 
Oxyrhina,  Galeocerdo,  Lamna  and  Ptychodus.  Among  the 
osseous  fishes,  Beryx,  Enchodus,  Portheus  and  Saurocephalus 
were  especially  common,  while  the  most  important  genus  of 
Ganoids  was  Lepidolus. 

The  Tertiary  fishes  are  nearly  all  of  modern  types,  and  from 
the  beginning  of  this  period  there  was  comparatively  little 
change.  In  the  marine  beds,  Sharks,  Rays  and  Chimasroids 
maintained  their  supremacy,  although  Teleosts  were  abundant, 
and  many  of  them  of  large  size.  The  Ganoids  were  compara- 
tively few  in  number.  In  the  earliest  Eocene  fresh-water 
deposits,  it  is  interesting  to  find  that  the  modern  Gar-pike, 
and  Amia,  the  Dog-fish  of  our  western  lakes,  which  by  their 
structure  are  seen  to  be  remnants  of  a  very  early  type,  are 
well  represented  by  species  so  closely  allied  to  them  that  only 
an  anatomist  could  separate  the  ancient  from  the  modern.  In 
the  succeeding  beds,  these  fishes  are  still  abundant,  and  with 
them  are  Siluroids  nearly  related  to  the  modern  Cat-fish 


(Pimelodus).  Many  small  fishes,  allied  apparently  to  the 
modern  herring  (Cfapea),  left  their  remains  in  great  numbers 
in  the  same  deposits,  and,  with  them  has  been  recently  found 
a  land-locked  Ray  (Heliobatis). 

The  almost  total  absence  of  remains  of  fishes  from  the  Mio- 
cene lake-basins  of  the  West  is  a  remarkable  fact,  and  perhaps 
may  best  be  explained  by  the  theory  that  these  inland  waters, 
like  many  of  the  smaller  lakes  in  the  same  region  to-day,  were 
so  impregnated  with  mineral  matters  as  to  render  the  existence 
of  vertebrate  life  in  them  impossible.  No  one  who  has  tasted 
such  waters,  or  has  attempted  to  ford  one  of  the  modern  alkaline 
lakes  which  are  often  met  with  on  the  present  surface  of  the 
same  deposits,  will  doubt  the  efficiency  of  this  cause,  or  the 
easy  entombment  of  trie  higher  vertebrates  that  ventured  within 
their  borders.  Tn  the  Pliocene  lake-basins  of  the  same  region, 
remains  of  fishes  were  not  uncommon,  and  in  some  of  them  are 
very  numerous.  These  are  all  of  modern  types,  and  most  of 
them  are  Cyprinoids,  related  to  the  modern  Carp.  The  Post- 
pliocene  fishes  are  essentially  those  of  to-day. 

In  this  brief  synopsis  of  the  past  ichthyic  life  of  this  Conti- 
nent, I  have  mentioned  only  a  few  of  the  more  important  facts, 
but  sufficient,  I  trust,  to  give  an  outline  of  its  history.  Of  this 
history,  it  is  evident  that  we  have  as  yet  only  a  very  imperfect 
record.  We  have  seen  that  the  earliest  remains  of  fishes 
known  in  this  country,  are  from  the  lower  Devonian  ;  but  these 
old  fishes  show  so  great  a  diversity  of  form  and  structure,  as 
to  clearly  indicate  for  the  class  a  much  earlier  origin.  In  this 
connection,  we  must  bear  in  mind  that  the  two  lowest  groups 
of  existing  fishes  are  entirely  without  osseous  skeletons,  and 
hence,  however  abundant,  would  leave  no  permanent  record  in 
the  deposits  in  which  remains  of  fishes  are  usually  preserved. 
It  is  safe  to  infer,  from  the  knowledge  which  we  now  possess 
of  the  simpler  forms  of  life,  that  even  more  of  the  early  fishes 
were  cartilaginous,  or  so  destitute  of  hard  parts  as  to  leave  no 
enduring  traces  of  their  existence.  Without  positive  knowledge 
of  such  forms,  and  considering  the  great  diversity  of  those  we 


have,  it  would  seern  a  hopeless  task  at  present  to  attempt 
to  trace  successfully  the  genealogy  of  this  class.  One  line, 
however,  appears  to  be  direct,  from  our  modern  Gar-pike, 
through  the  lower  Eocene  Lepidosteus  to  the  Lepidotus  of  the 
Cretaceous,  and  perhaps  on  through  the  Triassic  Isbhypterus 
and  Carboniferous  Palceoniscus  ;  but  beyond  this,  in  our  rocks, 
it  is  lost.  The  living  Chimaera  of  our  Pacific  coast  has  nearly 
allied  forms  in  the  Tertiary  and  Cretaceous,  more  distant  rela- 
tives in  the  Carboniferous,  and  a  possible  ancestor  in  the 
Devonian  Rhynchodus.  Our  Sharks  likewise  can  be  traced 
with  some  certainty  back  to  the  Palaeozoic ;  and  even  the 
Lepidosiren,  of  South  America,  although  its  immediate  pre- 
decessors are  unknown,  has  some  peculiar  characters  which 
strongly  point  to  a  Devonian  ancestry.  These  suggestive  lines 
indicate  a  rich  field  for  investigation  in  the  ancient  life-history 
of  American  fishes. 

The  Amphibians,  the  next  higher  class  of  vertebrates,  are  so 
closely  related  to  the  fishes  in  structure,  that  some  peculiar 
forms  of  the  latter  have  been  considered  by  anatomists  as 
belonging  to  this  group.  The  earliest  evidence  of  Amphibian 
existence,  on  this  continent,  is  in  the  Sub-Carboniferous,  where 
foot-prints  have  been  found  which  were  probably  made  by 
Labyrinthodonts,  the  most  ancient  representatives  of  the  class. 
Well  preserved  remains  are  abundant  in  the  Coal  Measures, 
and  show  that  the  Labyrinthodonts  differed  in  important  par- 
ticulars from  all  modern  Amphibians,  the  group  which  includes 
our  frogs  and  salamanders.  Some  of  these  ancient  animals 
resembled  a  salamander  in  shape,  while  others  were  serpent-like 
in  form.  None  of  those  yet  discovered  were  frog-like,  or  without 
a  tail,  although  the  restored  Labyrinthodont  of  the  text  books 
is  thus  represented.  All  were  protected  by  large  pectoral 
bony  plates,  and  an  armor  of  small  scutes  on  the  ventral  surface 
of  the  body.  The  walls  of  their  teeth  were  more  or  less  folded 
whence*  the  name  Labyrinthodont.  The  American  Amphib- 
ians known  from  osseous  remains  are  all  of  moderate  size, 
but  the  foot-prints  attributed  to  this  group  indicate  animals 
2 


10 

larger  than  any  of  the  class  yet  found  in  the  old  world.  The 
Carboniferous  Amphibians  were  abundant  in  the  swampy  trop- 
ical forests  of  that  period,  and  their  remains  have  been  found 
imbedded  in  the  coal  then  deposited,  as  well  as  in  hollow 
stumps  of  the  trees  left  standing. 

The  principal  genera  of  this  group  from  American  Car- 
boniferous rocks,  are,  Sauropus,  known  only  from  footprints, 
Baphetes,  Dendrerpeton,  Hylonomus,  Hylerpeton,  Raniceps,  Pelion, 
Leptophradus,  Molgophis,  Plyonius,  Amphibamus,  Cocytinus,  and 
Ceraterpeton.  The  last  genus  occurs  also  in  Europe.  Certain  of 
these  genera  have  been  considered  by  some  writers  to  be  more 
nearly  related  to  the  Lizards,  among  true  reptiles.  Some  other 
genera  known  from  fragmentary  remains  or  footprints  in  this 
formation  have  likewise  been  referred  to  the  true  reptiles,  but 
this  question  can  perhaps  be  settled  only  by  future  discoveries. 

~$o  Amphibia  are  known  from  American  Permian  strata,  but 
in  the  Triassic,  a  few  characteristic  remains  have  been  found. 
The  three  genera,  Dictyocephalus,  Dispelor  and  Pariostegus,  have 
been  described,  but,  although  apparently  all  Labyrintho- 
donts,  the  remains  preserved  are  not  sufficient  to  add  much  to 
our  knowledge  of  the  group.  The  Triassic  foot-prints  which 
have  been  attributed  to  Amphibians  are  still  more  unsatis- 
factory, and  at  present  no  important  conclusions  in  regard  to 
this  class  can  be  based  upon  them.  From  the  Jurassic  and 
Cretaceous  beds  of  this  Continent,  no  remains  of  Amphibians 
are  known.  A  few  only  have  been  found  in  the  Tertiary, 
and  these  are  all  of  modern  types. 

The  Amphibia  are  so  nearly  allied  to  the  Ganoid  fishes,  that 
we  can  hardly  doubt  their  descent  from  some  member  of  that 
group.  With  our  present  limited  knowledge  of  the  extinct 
forms,  however,  it  would  be  unprofitable  to  attempt  to  trace  in 
detail  their  probable  genealogy. 

The  authors  to  whom  especial  credit  is  due  for  our  knowl- 
edge of  American  fossil  Fishes  and  Amphibians,  are  New- 
berry,  Leidy,  Cope,  Dawson,  Agassiz,  St.  John,  Gibbes,  Wy- 
man,  Kedfield,  and  Emmons,  and  the  principal  literature  of  the 
subject  will  be  found  in  their  publications. 


11 

Reptiles  and  Birds  form  the  next  great  division  of  ver- 
tebrates, the  Sauropsida,  and  of  these  the  Reptiles  are  the  older 
type,  and  may  be  first  considered.  While  it  may  be  stated 
with  certainty  that  there  is  at  present  no  evidence  of  the  exist- 
ence of  this  group  in  American  rocks  older  than  the  Car- 
boniferous, there  is  some  doubt  in  regard  to  their  appearance 
even  in  this  period.  Various  foot-prints  which  strongly  resem- 
ble those  made  by  Lizards ;  a  few  well  preserved  remains  similar 
to  the  corresponding  bones  in  that  group;  and  a  few  charac- 
teristic specimens,  nearly  identical  with  those  from  another 
order  of  this  class,  are  known  from  American  Coal  Measures. 
These  facts,  and  some  others  which  point  in  the  same  direction, 
render  it  probable  that  we  may  soon  have  conclusive  evidence  of 
the  presence  of  true  Reptiles  in  this  formation,  and  in  our  over- 
lying Permian,  which  is  essentially  a  part  of  the  same  series. 
In  the  Permian  rocks  of  Europe,  true  Reptiles  have  been 
found. 

The  Mesozoic  Period  has  been  called  the  Age  of  Reptiles, 
and  during  its  continuance  some  of  the  strangest  forms  of  rep- 
tilian life  made  their  appearance,  and  became  extinct.  Near 
its  commencement,  while  trie  Triassic  shales  and  sandstones 
were  being  deposited,  true  reptiles  were  abundant.  Among 
the  most  characteristic  remains  discovered  are  those  of  the 
genus  Belodon,  which  is  well  known  also  in  the  Trias  of 
Europe.  It  belongs  to  the  Thecodont  division  of  Reptiles, 
which  have  teeth  in  distinct  sockets,  and  its  nearest  affinities 
are  with  the  Crocodilia,  of  which  order  it  may  be  considered 
the  oldest  known  representative.  In  the  same  strata  in  which 
the  Belodonts  occur,  remains  of  Dinosaurs  are  found,  and  it  is 
a  most  interesting  fact  that  these  highest  of  reptiles  should  make 
their  appearance,  even  in  a  generalized  form,  at  this  stage  of 
the  earth's  history.  The  Dinosaurs,  although  true  reptiles  in 
all  their  more  important  characters,  show  certain  well  marked 
points  of  resemblance  to  existing  birds  of  the  order  RatilcK,  a 
group  which  includes  the  Ostriches ;  and  it  is  not  improbable 
that  they  were  the  parent  stock  from  which  birds  originated. 


12 

During  Triassic  time,  the  Dinosaurs  attained  in  America  an 
enormous  development  both  in  variet}T  of  forms  and  in  size. 
Although  comparatively  few  of  their  bones  have  as  yet 
been  discovered  in  the  rocks  of  this  country,  they  have  left 
unmistakable  evidence  of  their  presence  in  the  foot-prints  and 
other  impressions  upon  the  shores  of  the  waters  which  they 
frequented.  The  Triassic  sandstone  of  the  Connecticut  Valley 
has  long  been  famous  for  its  fossil  foot-prints,  especially  the 
so-called  "bird-tracks,"  which  are  generally  supposed  to  have 
been  made  by  birds,  the  tracks  of  which  many  of  them  closely 
resemble.  A  careful  investigation,  however,  of  nearly  all  the 
specimens  yet  discovered,  has  convinced  me  that  there  is  not  a 
particle  of  evidence  that  any  of  these  fossil  impressions  were 
made  by  birds.  Most  of  these  three-toed  tracks  were  certainly 
not  made  by  birds ;  but  by  quadrupeds,  which  usually  walked 
upon  their  hind  feet  alone,  and  only  occasionally  put  to  the 
ground  their  smaller  anterior  extremities.  I  have  myself 
detected  the  impressions  of  these  anterior  limbs  in  connection 
with  the  posterior  foot-prints  of  nearly  all  of  the  supposed 
"  bird-tracks"  described,  and  have  little  doubt  that  they  will 
eventually  be  found  with  all.  These  double  impressions  -are 
precisely  the  kind  which  Dinosaurian  reptiles  would  make, 
and  as  the  only  characteristic  bones  yet  found  in  the  same 
rocks  belong  to  animals  of  this  group,  it  is  but  fair  to  attribute 
ail  these  foot-prints  to  Dinosaurs,  even  where  no  impressions 
of  fore-feet  have  been  detected,  until  some  evidence  appears 
that  they  were  made  by  Birds.  I  have  no  doubt  that 
Birds  existed  at  this  time,  although  at  present  the  proof  is 
wanting. 

The  principal  genera  of  Triassic  Reptiles  known  from  osseous 
remains  in  this  country  are,  Amphisaurus  (Meyadactylus), 
from  the  Connecticut  Valley,  Bathygnathus,  from  Prince  Ed- 
ward's Island,  Belodon  and  Clepsysaurus.  Other  generic  names 
which  have  been  applied  to  foot-prints  and  to  fragmentary 
remains,  need  not  be  here  enumerated,  A  few  remains  of 
Reptiles  have  been  found  in  undoubted  Jurassic  rocks  of 


13 

America,  but  they  are  not  sufficiently  well  determined  to  be 
of  service  in  this  connection.  Others  have  been  reported  from 
supposed  Jurassic  strata,  which  are  now  known  to  be  Creta- 
ceous. It  will  thus  be  seen  that,  although  reptilian  life  was 
especially  abundant  during  the  Triassic  and  Jurassic  periods, 
bat  few  bones  have  been  found.  This  is  owing  in  part  to  the 
character  of  most  of  the  rocks  then  formed,  which  were  not 
well  fitted  for  preserving  such  remains,  although  admirably 
adapted  to  retain  foot-prints. 

During  the  Cretaceous  Period,  Reptilian  life  in  America 
attained  its  greatest  development,  and  the  sediments  laid  down 
in  the  open  seas  and  estuaries  were  usually  most  favorable  for 
the  preservation  of  a  faithful  record  of  its  various  phases.  With- 
out such  a  perfect  matrix  as  some  of  these  deposits  afford,  many 
of  the  most  interesting  vertebrates  recently  brought  to  light 
from  this  formation  would  probably  have  remained  unknown. 
The  vast  extent  of  these  beds  ensures,  moreover,  many  future 
discoveries  of  interest. 

In  the  lowest  Cretaceous  strata  of  the  Rocky  Mountain 
region,  the  Dakota  group,  part  of  which  at  least  represents 
the  Wealden  of  Europe,  remains  of  Chelonia,  or  Turtles,  Croc- 
odiles, and  Dinosaurs  occur,  the  last  being  especially  abun- 
dant. The  Chelonia,  although  known  from  the  Jurassic  of 
Europe,  here  appear  for  the  first  time  in  American  rocks. 
Some  of  the  earliest  forms  are  allied  to  the  modern  genus 
Trionyx.  In  the  higher  Cretaceous  beds,  some  Chelonians  of 
enormous  size  have  been  found.  They  belong  to  the  genus 
Atlantochelys,  which  has  the  ribs  separate,  as  in  the  existing 
Spharyis,  and  presents  other  embryonic  characters.  A  few 
genera  appear  to  be  related  to  the  modern  genus  Chelone.  The 
remaining  Cretaceous  species  were  mostly  of  the  Emydoid 
type  ;  and  others  were  related  to  Chelydra.  The  more  important 
genera  of  Cretaceous  Chelonians  known  from  characteristic  speci- 
mens are,  Allan tochelys  (Protostega),  Adocus,  Sothremys,  Coinpse- 
mys,  Plastomenus,  Osteopygis,  Propleura,  Lytoloma,  and  Taphros- 
phys.  Most  of  these  genera  were  represented  by  several  species, 


14 

and  the  individuals  were  numerous.  No  land  Tortoises  have  as 
yet  been  found  in  this  formation.  In  American  Tertiary  depos- 
its, Ohelonians  are  abundant,  especially  in  the  fresh-water  beds. 
They  all  show  near  affinities  with  modern  types,  and  most  of 
them  can  be  referred  to  existing  genera.  In  the  Tertiary  lake- 
basins  of  the  West,  land  Tortoises  are  very  numerous,  and 
with  them  are  many  fresh-water  forms  of  Trionyx  and  allied 
genera. 

A  striking  feature  of  the  American  Cretaceous  fauna,  as  con- 
trasted with  that  of  Europe,  is  the  almost  entire  absence  in  our 
strata  of  species  of  Ichthyosaurus  and  Plesiosaurus,  which 
abound  in  many  other  regions,  but  here  seem  to  be  replaced  by 
the  Mosasaurs.  A  few  fragmentary  remains  have  indeed  been 
referred  to  these  genera,  but  the  determination  may  fairly  be 
questioned.  This  is  more  than  true  of  the  proposed  new  order 
Streptosauria,  which  was  founded  wholly  on  error.  The  order 
Plesiosauria,  however,  is  well  represented,  but  mainly  by  forms 
more  nearly  related  to  the  genus  Pliosaurus  than  to  the  type 
of  the  group.  These  were  marine  reptiles,  all  of  large  size, 
while  some  of  them  attained  vast  dimensions.  So  far  as  at 
present  identified,  they  may  be  referred  to  the  genera,  Cimalio- 
saurus,  Discosaurus  (Elasmosaurus),  and  Pliosaurus.  The  num- 
ber of  species  is  comparatively  few,  and  none  are  known  above 
the  Cretaceous.  The  important  suggestion  of  Gegenbaur,  that 
the  Halisauria,  which  include  the  Plesiosaurs,  branched  off 
from  the  Fishes  before  the  Amphibians,  finds  some  support  in 
American  specimens  recently  discovered. 

The  Reptiles  most  characteristic  of  our  American  Cretaceous 
strata  are  the  Mosasauria,  a  group  with  very  few  representatives 
in  other  parts  of  the  world.  In  our  Cretaceous  seas,  they  ruled 
supreme,  as  their  numbers,  size,  and  carnivorous  habits,  enabled 
them  to  easily  vanquish  all  rivals.  Some  were  at  least  sixty 
feet  in  length,  and  the  smallest  ten  or  twelve.  In  the  inland 
Cretaceous  sea  from  which  the  Rocky  Mountains  were  begin- 
ning to  emerge,  these  ancient  " Sea  Serpents"  abounded;  and 
many  were  entombed  in  its  muddy  bottom.  On  one  occasion, 


15 

as  I  rode  through  a  valley  washed  out  of  this  old  ocean  bed,  I 
saw  no  less  than  seven  different  skeletons  of  these  monsters  in 
sight  at  once.  The  Mosasaurs  were  essentially  swimming  Liz- 
ards, with  four  well  developed  paddles,  and  they  had  little  affin- 
ity with  modern  serpents,  to  which  they  have  been  compared. 
The  species  are  quite  numerous,  but  they  belong  to  compara- 
tively few  genera,  of  which  Mosasaurus,  Tylosaurus,  Lestosaurus 
and  Edestosaurus,  have  alone  been  identified  with  certainty.  The 
genus  Mosasaurus  was  first  found  in  Europe.  All  the  known 
species  of  the  group  are  Cretaceous. 

The  Crocodilia  are  abundant  in  rocks  of  Cretaceous  age  in 
America,  and  two  distinct  types  are  represented.  The  older 
type,  which  is  foreshadowed  by  Belodon  of  the  Trias,  has  bicon- 
cave vertebrae,  and  shows  marked  affinities  with  the  genus 
Teleosaurus,  from  the  Jura  of  Europe.  The  best  known 
genus  is  Hyposaurus,  of  which  there  are  several  species,  all 
more  or  less  resembling  in  form  the  modern  Gavial  of  the 
Ganges.  A  peculiar  intermediate  form  is  seen  in  Diplosaurus, 
from  the  Wealden  of  the  Rocky  Mountains.  The  second  type, 
which  now  makes  its  appearance  for  the  first  time,  has  pro- 
ccelian  vertebrae,  and  in  other  respects  resembles  existing  Croc- 
odiles. The  genera  described  are  Bottosaurus,  Holops  and  Tho- 
racosaurus,  none  of  which,  so  far  as  known,  pass  above  the 
Cretaceous.  Of  Crocodilia  with  opisthoccelous  vertebras,  Amer- 
ica, so  far  as  we  know,  has  none.  Specimens  similar  to  those 
so  termed  in  Europe,  are  not  uncommon  here,  but  they  per- 
tain to  Dinosaurs. 

In  the  Eocene  fresh-water  beds  of  the  West,  Crocodilians 
are  especially  abundant,  and  all,  with  the  exception  of  Limno- 
saurus,  belong  apparently  to  the  genus  Crocodilus,  although 
some  species  show  certain  points  of  resemblance  to  existing 
Alligators.  The  Miocene  lake-basins  of  the  same  region 
contain  no  remains  of  Crocodiles,  so  far  as  known,  and  the 
Pliocene  deposits  have  afforded  only  a  single  species.  The 
Tertiary  marine  beds  of  the  Atlantic  Coast  contain  com- 
paratively few  Crocodilian  remains,  and  all  are  of  modern 


.  16 

types ;  the  genus  Oavialis  having  one  Eocene  species,  and  the 
Alligator  being  represented  only  in  the  latest  deposits. 

It  is  worthy  of  special  mention  in  this  connection,  that  no 
true  Lacertilia,  or  Lizards,  and  no  Ophidia,  or  Serpents,  have 
yet  been  detected  in  American  Cretaceous  beds ;  although  their 
remains,  if  present,  would  hardly  have  escaped  observation  in 
the  regions  explored.  The  former  will  doubtless  be  found,  as 
several  species  occur  in  the  Mesozoic  of  Europe  ;  and  perhaps 
the  latter,  although  the  Ophidians  are  apparently  a  more  mod- 
ern type.  In  the  Eocene  lake-basins  of  Western  America,  re- 
mains of  Lizards  are  very  numerous,  and  indicate  species  much 
larger  than  any  existing  to-day.  Some  of  these,  the  Glyptosau- 
ridan,  were  protected  by  a  highly  ornamented  bony  coat  of  mail, 
and  others  were  covered  with  scales,  like  recent  Lizards.  A 
few  resembled,  in  their  more  important  characters,  the  modern 
Iguana.  The  genera  best  represented  in  the  Eocene,  are,  Gtyp- 
tosaurus,  Iguanavus,  Oreosaurus,  Thinosaurus,  Tinosaurus  and 
Saniva.  Some  of  these  genera  appear  to  have  continued  into  the 
Miocene,  but  here,  as  well  as  in  the  Pliocene,  few  remains  of 
this  group  have  been  found.  It  is  not  improbable  that  some 
of  our  extinct  Eeptiles  may  prove  to  belong  to  Rynchocephala, 
but  at  present  this  is  uncertain.  The  genus  Notosaurus,  from 
Brazil,  has  biconcave  vertebras,  and  some  other  characters 
which  point  to  that  group.  No  Dicynodonts  or  Theriodonts 
have  as  yet  been  found  in  this  country. 

The  first  American  Serpents,  so  far  as  now  known,  appear 
in  the  Eocene,  which  contains  also  the  oldest  European  species. 
On  the  Atlantic  border,  the  genus  Titanophis  (Dinophis)  is 
represented  by  several  species  of  large  size,  one  at  least  thirty 
feet  in  length,  and  all  doubtless  inhabitants  of  the  sea.  In  the 
fresh-water  Western  Eocene,  remains  of  snakes  are  abundant, 
but  all  are  of  moderate  size.  The  largest  of  these  were  related 
to  the  modern  Boa  Constrictors.  The  genera  described  are 
Soavus,  Liihophis  and  Limnophis.  The  Miocene  and  Pliocene 
Snakes  from  the  same  region  are  known  only  from  a  few  frag- 
mentary remains. 


17 

The  Pterosauria,  or  flying  Lizards,  are  among  the  most 
interesting  Reptiles  of  Mesozoic  time,  and  many  of  them  left 
their  remains  in  the  soft  sediments  of  our  inland  Cretaceous 
sea.  These  were  veritable  Dragons,  having  a  spread  of  wings 
of  from  ten  to  twenty-five  feet.  They  differed  essentially  from 
the  smaller  Pterodactyls  found  in  the  old  world,  in  the  entire 
absence  of  teeth,  showing  in  this  respect  a  resemblance  to 
modern  birds ;  and  they  possess  other  distinctive  characters. 
They  have  therefore  been  placed  in  a  new  order,  Pteranodontia, 
from  the  typical  genus  Pteranodon,  of  which  five  species  are 
known.  The  only  other  genus  is  Nyctosaurus,  represented  by  a 
single  species.  All  the  specimens  yet  found  are  from  essen- 
tially the  same  horizon,  in  the  Chalk  of  Kansas.  The  reported 
discovery  of  remains  of  this  order  from  older  formations  in  this 
country  is  without  foundation. 

The  strange  Reptiles  known  as  Dinosauria,  which,  as  we 
have  seen,  were  numerous  during  the  deposition  of  our  Triassic 
shales  and  sandstones,  have  not  yet  been  found  in  American 
Jurassic,  but  were  well  represented  here  throughout  the  Cre- 
taceous, and  at  its  close  became  extinct.  These  animals  possess 
a  peculiar  interest  to  the  anatomist,  since,  although  reptilian 
in  all  their  main  characters,  they  show  clear  affinities  with 
the  Birds,  and  have  some  features  which  may  point  to  Mammals. 
The  Cretaceous  Dinosaurs  were  all  of  large  size,  and  most  of 
them  walked  on  the  hind  feet  alone,  like  modern  Struthious 
birds.  Two  well  marked  types  may  be  distinguished  among 
the  remains  discovere:!  in  deposits  of  this  age :  the  herbiv- 
orous forms,  represented  mainly  by  Hadrosaurus,  a  near  ally  of 
the  Iguanodon  of  Europe ;  and  their  carnivorous  enemies,  of 
Which  Dryptosaurus  (Lcelaps)  may  be  considered  typical  in  this 
country,  and  Megalosaurus  in  Europe.  Near  the  base  of  our 
Cretaceous  formation,  in  beds  which  I  regard  as  the  equivalent 
of  the  European  Wealden,  the  most  gigantic  forms  of  this 
order  yet  discovered  have  recently  been  brought  to  light.  One 
of  these  monsters  (Titanosaurus  montanus),  from  Colorado,  is 
by  far  the  largest  land  animal  yet  discovered;  its  dimensions 
3 


18 

being  greater  than  was  supposed  possible,  in  an  animal  that 
lived  and  moved  upon  the  land.  It  was  some  fifty  or  sixty 
feet  in  length,  and,  when  erect,  at  least  thirty  feet  in  height. 
It  doubtless  fed  upon  the  foliage  of  the  mountain  forests, 
portions  of  which  are  preserved  with  its  remains.  With  Titan- 
osaurus,  the  bones  of  smaller  Dinosaurs,  one  (Nanosaurus)  not 
larger  than  a  Cat,  as  well  as  those  of  Crocodiles  and  Turtles, 
are  not  uncommon.  The  recent  discovery  of  these  interesting 
remains,  many  and  various,  in  strata  that  had  long  been  pro- 
nounced by  professional  explorers  barren  of  vertebrate  fossils, 
should  teach  caution  to  those  who  decline  to  accept  the  imper- 
fection of  our  knowledge  to-day  as  a  fair  plea  for  the  supposed 
absence  of  intermediate  forms. 

In  the  marine  Cretaceous  beds  of  the  West,  only  a  single 
Dinosaur  {Hadrosaurus  agilis),  has  been  found,  but  in  the  higher 
fresh-water  beds,  which  mark  the  close  of  this  formation,  their 
remains  are  numerous,  and  indicate  several  well  marked  species, 
if  not  genera.  In  the  marine  beds  on  the  Atlantic  Coast,  the 
bones  of  Dinosaurs  are  frequently  met  with,  and  in  the  Upper 
Cretaceous  Green  sand  of  New  Jersey,  the  type  specimens  of 
Hadrosaurus  and  Dryptosaurus  were  found.  In  Cretaceous 
fresh-water  deposits  on  the  coast  of  Brazil,  remains  of  this  order 
occur,  but  the  specimens  hitherto  discovered  are  not  sufficiently 
characteristic  for  accurate  determination.  This  is  unfortunately 
true  of  many  Dinosaurian  fossils  from  North  America,  but  the 
great  number  of  these  Eeptiles  which  lived  here  during  the 
Cretaceous  Period  promises  many  future  discoveries,  and  sub- 
stantial additions  to  our  present  knowledge  of  the  group. 

The  first  appearance  of  Birds  in  America,  according  to  our 
present  knowledge,  was  during  the  Cretaceous  Period,  although 
many  announcements  have  been  made  of  their  existence  in 
preceding  epochs.  The  evidence  of  their  presence  in  the  Trias, 
based  on  footprints  and  other  impressions,  is,  at  present,  as  we 
have  seen,  without  value;  although  we  may  confidently  await 
their  discovery  there,  if  not  in  older  formations.  Archwopteryx, 
from  the  European  Jura,  the  oldest  bird  known,  and  now 


19 

fortunately  represented  by  more  than  a  single  specimen, 
clearly  indicates  a  much  higher  antiquity  for  the  class.  The 
earliest  American  forms,  at  present  known,  are  the  Odontornithes, 
or  Birds  with  teeth,  which  have  been  exhumed  within  the  last 
few  years,  from  the  Chalk  of  Kansas.  The  two  genera,  Hes- 
perornis and  Ichthyornis,  are  types  of  distinct  orders,  and  differ 
from  each  other  and  from  Archceopteryx  much  more  than  do 
any  existing  birds  among  themselves ;  thus  showing  that  Birds 
are  now  a  closed  type,  and  that  the  key  to  the  history  of  the 
class  must  be  sought  for  in  the  distant  past. 

In  Hesperornis,  we  have  a  large  aquatic  bird,  nearly  six  feet 
in  length,  with  a  strange  combination  of  characters.  The  jaws 
are  provided  with  teeth,  set  in  grooves ;  the  wings  were  rudi- 
mentary, and  useless ;  while  the  legs  were  very  similar  to  those 
of  modern  diving  birds.  This  last  feature  was  merely  an  adap- 
tation, as  the  more  important  characters  are  Struthious,  showing 
that  Hesperornis  was  essentially  a  carnivorous  swimming  Ostrich. 
Ichthyornis,  a  small  flying  bird,  was  stranger  still,  as  the  teeth 
were  in  sockets;  and  the  vertebrae  biconcave,  as  in  Fishes, 
and  a  few  Reptiles.  Apatornis  and  other  allied  forms  occur 
in  the  same  beds,  and  probably  all  were  provided  with  teeth. 
It  is  strange  that  the  companions  of  these  ancient  toothed 
Birds  should  have  been  Pterodactyls  without  teeth.  In  the 
later  Cretaceous  beds  of  the  Atlantic  Coast,  various  remains 
of  aquatic  Birds  have  been  found,  but  all  are  apparently  dis- 
tinct from  those  of  the  West.  The  known  genera  of  Ameri- 
can Cretaceous  birds  are,  Apatornis,  Baptornis,  Graculavus, 
Hesperornis,  Ichthyornis,  Laornis,  Lesiornis,  Palceotringa  and 
Telmatornis.  These  are  represented  by  some  twenty  species. 
In  Europe,  but  two  species  of  Cretaceous  birds  are  known, 
and  both  are  based  upon  fragmentary  specimens. 

During  the  Tertiary  period,  Birds  were  numerous  in  this 
country,  and  all  yet  discovered  appear  to  have  belonged  to 
modern  types.  The  Eocene  species  described  are  mostly  wading 
birds,  but  here,  and  in  the  later  Tertiary  deposits,  some  charac- 
teristic American  forms  make  their  appearance,  strongly  fore- 


20 

shadowing  oar  present  aviari  fauna.  The  extinct  genera  are  the 
Eocene  Uintornis,  related  to  the  Woodpeckers,  and  Aletornis, 
which  includes  several  species  of  Waders.  Among  the  existing 
genera  found  in  our  Tertiary  beds  are,  A  guild.  Bubo,  Meleagris, 
Grus,  Graculus,  Pujfinus,  and  Catarractes.  The  Great  Auk 
(Alca  impennis),  which  was  once  very  abundant  on  our  North- 
east Coast,  has  become  extinct  within  a  few  years. 

In  this  brief  summary  of  the  past  life  of  Eeptiles  and  Birds 
in  America,  I  have  endeavored  to  exclude  doubtful  forms,  and 
those  very  imperfectly  known,  preferring  to  present  the  conclu- 
sions reached  by  careful  study,  incomplete  though  they  be,  rather 
than  weary  you  with  a  descriptive  catalogue  of  all  the  fossils 
to  which  names  have  been  applied.  Even  this  condensed 
review  can  hardly  fail  to  give  you  some  conception  of  the 
wealth  of  our  continent  in  the  extinct  forms  of  these  groups, 
and  thus  to  suggest  what  its  actual  life  must  have  been. 

Although  the  Trias  offers  at  present  the  first  unquestioned 
evidence  of  true  Reptiles,  we  certainly  should  not  be  justified 
in  supposing  for  a  moment  that  older  forms  did  not  exist.  So 
too  in  considering  the  different  groups  of  Reptiles,  which  seem 
to  make  their  first  appearance  at  certain  horizons,  flourish- for 
a  time,  and  then  decline,  or  disappear,  every  day  brings  evidence 
to  show  that  they  are  but  fragments  of  the  unraveled  strands 
which  converge  in  the  past  to  form  the  mystic  cord  uniting  all 
life.  If  the  attempt  is  made  to  follow  back  any  single  thread, 
and  thus  trace  the  lineage  of  a  group,  we  are  met  by  difficulties 
which  the  science  of  to-day  can  only  partially  remove.  And  yet 
the  anatomist  constantly  sees  in  the  fragments  which  he  studios 
hints  of  relationship  which  are  to  him  sure  prophecies  of  future 
discoveries. 

The  genealogy  of  the  Chelonia  is  at  present  unknown,  and 
our  American  extinct  forms,  so  far  as  we  now  have  them, 
throw  little  light  on  their  ancestry.  This  is  essentially  true, 
also,  of  our  Plesiosauria,  Lacertilia  and  Ophidia,  although  sug- 
gestive facts  are  not  wanting  to  indicate  possible  lines  of 
descent.  With  the  Crocodilia,  however,  the  case  seems  to  be 


21 

different,  and  Huxley  has  clearly  pointed  out  the  path  for 
investigation.  It  is  probable  that  material  already  exists  in 
our  museums  for  tracing  the  group  through  several  important 
steps  in  its  development.  We  have  already  seen  that  the 
modern  procoelian  type  of  this  order  goes  back  only  to  the 
Upper  Cretaceous,  while  the  Belodonts,  of  our  Triassic  rocks, 
with  their  biconcave  vertebras,  are  the  oldest  known  Croco- 
dilians.  Our  Jurassic,  unfortunately,  throws  but  little  light  on 
the  intermediate  forms,  but  we  know  that  the  line  was  con- 
tinued, as  it  was  in  the  old  world  through  Tekosaurus.  The 
beds  of  the  Rocky  Mountain  Wealden  have  just  furnished  us 
with  a  genuine  "missing  link,"  a  saurian  (Diplosaurus)  with 
essentially  the  skull  and  teeth  of  a  modern  Crocodile,  and  the 
vertebras  of  its  predecessor  from  the  Trias.  This  peculiar  rep- 
tile clearly  represents  an  important  stage  in  the  progressive 
series,  and  evidently  one  soon  after  the  separation  of  the  Croc- 
odile branch  from  the  main  stem.  The  modern  Gavial  type 
appears  to  have  been  developed  about  the  same  time,  as  the  form 
was  well  established  in  the  Upper  Cretaceous  genus,  Thoraco- 
saurus.  The  Teleosaurian  group,  with  biconcave  vertebrae, 
evidently  the  parent  stock  of  Crocodilians,  became  extinct  with 
Hyposaurus  of  the  same  horizon,  leaving  the  Crocodile  and 
Gavial,  with  their  more  perfect  procoelian  vertebrae,  to  contend 
for  the  supremacy.  In  the  early  Eocene,  both  of  these  types 
were  abundant,  but  some  of  the  Crocodiles  possessed  characters 
pointing  towards  the  Alligators,  which  do  not  appear  to  have 
been  completely  differentiated  until  later. 

Nothing  is  really  known  to-day  of  the  earlier  genealogy  of 
the  Pterosauria,  but  our  American  forms,  without  teeth,  are 
clearly  the  last  stage  in  their  development  before  this  peculiar 
group  became  extinct.  The  oldest  European  form,  Dimorphodon, 
from  the  Lower  Lias,  had  the  entire  jaws  armed  with  teeth,  and 
was  provided  with  a  long  tail.  The  later  genus  Pterodactylus 
retained  the  teeth,  but  had  essentially  lost  the  tail ;  while 
Ramphorhynchus  had  retained  the  elongated  tail,  but  had  lost 
the  teeth  from  the  fore  part  of  both  jaws.  In  the  genus  Pterano- 


22 

don  from  the  American  Cretaceous,  the  teeth  are  entirely  absent, 
and  the  tail  is  a  mere  rudiment.  In  the  gradual  loss  of  the 
teeth  and  tail,  these  reptiles  followed  the  same  path  as  Birds,  and 
might  thus  seem  to  approach  them,  as  many  have  supposed. 
This  resemblance,  however,  is  only  a  superficial  one,  as  a  study 
of  the  more  important  characters  of  the  Pterodactyls  shows 
that  they  are  an  aberrant  type  of  Reptiles,  totally  oft'  the  line 
through  which  the  Birds  were  developed.  The  announcement 
made  not  long  since  in  Europe,  and  accepted  by  some  American 
authors,  that  the  Plerosauria,  in  consequence  of  certain  points 
in  their  structure,  were  essentially  Birds,  is  directly  disproved 
by  American  specimens,  far  more  perfect  than  those  on  which 
the  conclusion  was  based. 

It  is  now  generally  admitted  by  biologists  who  have  made 
a  study  of  the  vertebrates,  that  Birds  have  come  down  to  us 
through  the  Dinosaurs,  and  the  close  affinity  of  the  latter 
with  recent  Struthious  Birds  will  hardly  be  questioned.  The 
case  amounts  almost  to  a  demonstration,  if  we  compare,  with 
Dinosaurs,  their  contemporaries,  the  Mesozoic  Birds.  The 
classes  of  Birds  and  Reptiles,  as  now  living,  are  separated  by  a 
gulf  so  profound  that  a  few  years  since  it  was  cited  by  the 
opponents  of  evolution  as  the  most  important  break  in  the 
animal  series,  and  one  which  that  doctrine  could  not  bridge 
over.  Since  then,  as  Huxley  has  clearly  shown,  this  gap 
has  been  virtually  filled  by  the  discovery  of  bird-like  Reptiles 
and  reptilian  Birds.  Compsognathus  and  Archceopteryx  of  the 
Old  World,  and  Ichihyornis  and  Hesperornis  of  the  New,  are 
the  stepping  stones  by  which  the  evolutionist  of  to-day  leads 
the  doubting  brother  across  the  shallow  remnant  of  the  gulf, 
once  thought  impassable. 

It  remains  now  to  consider  the  highest  group  of  the  Animal 
Kingdom,  the  class  Mammalia,  which  includes  Man.  Of  the 
existence  of  this  class  before  the  Trias  we  have  no  evidence, 
either  in  this  country  or  in  the  Old  World,  and  it  is  a  significant 
fact  that  at  essentially  the  same  horizon  in  each  hemisphere,  sim- 


23 

ilar  low  forms  of  Mammals  make  their  appearance.  Although 
only  a  few  incomplete  specimens  have  been  discovered,  they 
are  characteristic  and  well  preserved,  and  all  are  apparently 
Marsupials,  the  lowest  Mammalian  group  which  we  know  in 
this  country,  living  or  fossil.  The  American  Triassic  Mam- 
mals are  known  at  present  only  from  two  small  lower  jaws,  on 
which  is  based  the  genus  Dromotherium,  supposed  to  be  related 
to  the  insect-eating  Myrmecobius,  now  living  in  Australia. 

Although  the  Jura  of  Europe  has  yielded  other  similar 
Mammals,  we  have  as  yet  none  of  this  class  from  that  forma- 
tion ;  while,  from  rocks  of  Cretaceous  age,  no  Mammals  are 
known  in  any  part  of  the  world.  This  is  especially  to  be 
regretted,  as  it  is  evidently  to  the  Cretaceous  that  we  must 
look  for  the  first  representatives  of  many  of  our  present  groups 
of  Mammals,  as  well  as  for  indications  of  their  more  ancient 
lineage.  That  some  discovery  of  this  nature  from  the  Creta- 
ceous is  near  at  hand,  I  cannot  doubt,  when  I  consider  what  the 
last  few  years  have  brought  to  light  in  the  Eocene. 

In  the  lowest  Tertiary  beds  of  this  country,  a  rich  Mam- 
malian fauna  suddenly  makes  its  appearance,  and  from  that 
time  through  the  Age  of  Mammals  to  the  present,  America 
has  been  constantly  occupied  by  this  type  of  life  in  the  greatest 
diversity  of  form.  Fortunately,  a  nearly  continuous  record  of 
this  life,  as  preserved,  is  now  accessible  to  us,  and  ensures  great 
additions  to  our  knowledge  of  the  genealogy  of  Mammals,  and 
perhaps  the  solution  of  more  profound  problems.  Before  pro- 
ceeding to  discuss  in  detail  American  fossil  Mammalia,  it  is 
important  to  define  the  divisions  of  time  indicated  in  our 
Tertiary  and  Post-Tertiary  deposits,  as  these  in  many  cases 
mark  successive  stages  in  the  development  of  the  mammals. 

The  boundary  line  between  the  Cretaceous  and  Tertiary  in 
the  region  of  the  Eocky  Mountains  has  been  much  in  dispute 
during  the  last  few  years,  mainly  in  consequence  of  the  uncer- 
tain geological  bearings  of  the  fossil  plants  found  near  this  hori- 
zon. The  accompanying  invertebrate  fossils  have  thrown  little 
light  on  the  question,  which  is  essentially,  whether  the  great 


24 

Lignite  series  of  the  West  is  uppermost  Cretaceous,  or  lowest 
Eocene.  The  evidence  of  the  numerous  vertebrate  remains  is, 
in  my  judgment,  decisive,  and  in  favor  of  the  former  view. 

This  brings  up  an  important  point  in  Palaeontology,  one  to 
which  my  attention  was  drawn  several  years  since,  namely : 
the  comparative  value  of  different  groups  of  fossils  in  marking 
geological  time.  In  examining  the  subject  with  some  care,  I 
found  that,  for  this  purpose,  plants,  as  their  nature  indicates, 
are  most  unsatisfactory  witnesses;  that  invertebrate  animals 
are  much  better ;  and  that  vertebrates  afford  the  most  reliable 
evidence  of  climatic  and  other  geological  changes.  The  sub- 
divisions of  the  latter  group,  moreover,  and  in  fact  all  forms 
of  animal  life,  are  of  value  in  this  respect,  mainly  according 
to  the  perfection  of  their  organization,  or  zoological  rank. 
Fishes,  for  example,  are  but  slightly  affected  by  changes  that 
would  destroy  Reptiles  or  Birds,  and  the  higher  Mammals 
succumb  under  influences  that  the  lower  forms  pass  through 
in  safety.  The  more  special  applications  of  this  general  law, 
and  its  value  in  geology,  will  readily  suggest  themselves. 

The  evidence  offered  by  fossil  remains  is,  in  the  light  of  this 
law,  conclusive,  that  the  line,  if  line  there  be,  separating  .our 
Cretaceous  from  the  Tertiary,  must  at  present  be  drawn  where 
the  Dinosaurs  and  other  Mesozoic  vertebrates  disappear,  and 
are  replaced  by  the  Mammals,  henceforth  the  dominant  type. 

The  Tertiary  of  Western  America  comprises  the  most  exten- 
sive series  of  deposits  of  this  age  known  to  geologists,  and 
important  breaks  in  both  the  rocks  and  the  fossils  separate  it 
into  three  well-marked  divisions.  These  natural  divisions  are 
not  the  exact  equivalents  of  the  Eocene,  Miocene,  and  Pliocene 
of  Europe,  although  usually  so  considered,  and  known  by  the 
same  names ;  but,  in  general,  the  fauna  of  each  appears  to  be 
older  than  that  of  its  corresponding  representative  in  the  other 
hemisphere;  an  important  fact,  not  hitherto  recognized.  This 
partial  resemblance  of  our  extinct  faunas  to  others  in  regions 
widely  separated,  where  the  formations  are  doubtless  somewhat 
different  in  geological  age,  is  precisely  what  we  might  expect, 


25 

if,  as  was  probable,  the  main  migrations  took  place  from  this 
Continent.  It  is  better  at  once  to  recognize  this  principle, 
rather  than  attempt  to  bring  into  exact  parallelism,  formations 
that  were  not  strictly  contemporaneous. 

The  freshwater  Eocene  deposits  of  our  Western  Territories, 
which  are  in  the  same  region  at  least  two  miles  in  vertical 
thickness,  may  be  separated  into  three  distinct  subdivisions. 
The  lowest  of  these,  resting  unconformably  on  the  Cretaceous, 
has  been  termed  the  Vermilion  Creek,  or  Wahsatch,  Group.  It 
contains  a  well-marked  mammalian  fauna,  the  largest  and  most 
characteristic  genus  of  which  is  the  ungulate  Coryphodort,  and 
hence  I  have  called  these  deposits  the  Coryphodon  Beds.  The 
middle  Eocene  strata,  which  have  been  termed  the  Green 
River  arid  Bridger  Series,  may  be  designated  as  the  Dinoceras 
Beds,  as  the  gigantic  animals  of  this  order  are  only  found  here. 
The  uppermost  Eocene,  or  the  Uintah  Group,  is  especially 
well  characterized  by  large  mammals  of  the  genus  Diplacodon, 
and  hence  may  be  termed  the  Diplacodon  Beds.  The  fauna  of 
each  of  these  three  subdivisions  was  essentially  distinct,  and  the 
fossil  remains  of  each  were  entombed  in  different  and  successive 
ancient  lakes.  It  is  important  to  remember  that  these  Eocene 
lake-basins  all  lie  between  the  Eocky  Mountains  on  the  east 
and  the  Wahsatch  Range  on  the  west,  or  along  the  high 
central  plateau  of  the  Continent.  As  these  mountain  chains 
were  elevated,  the  enclosed  Cretaceous  sea,  cut  off  from  the 
ocean,  gradually  freshened,  and  formed  these  extensive  lakes, 
while  the  surrounding  land  was  covered  with  a  luxuriant  trop- 
ical vegetation,  and  with  many  strange  forms  of  animal  life. 
As  the  upward  movement  of  this  region  continued,  these  lake- 
basins,  which  for  ages  had  been  filling  up,  preserving  in  their 
sediments  a  faithful  record  of  Eocene  life-history,  were  slowly 
drained  by  the  constant  deepening  of  the  outflowing  rivers,  and 
they  have  since  remained  essentially  dry  land. 

The  Miocene  lake-basins  are  on  the  flanks  of  this  region, 
where  only  land  had  been  since  the  close  of  the  Cretaceous. 
These  basins  contain  three  faunas,  nearly  or  quite  distinct.  The 
4 


26 

lowest  Miocene,  which  is  only  found  east  of  the  Eocky  Moun- 
tains, alone  contains  the  peculiar  mammals  known  as  the  Bron- 
totheridce,  and  these  deposits  may  be  called  the  Brontotherium 
Beds.  The  strata  next  above,  which  represent  the  middle  Mio- 
cene, have  as  their  most  characteristic  fossil  the  genus  Oreodon, 
and  are  known  as  the  Oreodou  Beds.  The  upper  Miocene,  which 
occurs  in  Oregon,  is  of  great  thickness,  and  from  one  of  its  most 
important  fossils,  Miohippus,  may  be  designated  as  the  Miohip- 
pus  Series.  The  climate  here  during  this  period  was  warm 
temperate. 

Above  the  Miocene,  east  of  the  Eocky  Mountains  and  on  the 
Pacific  Coast,  the  Pliocene  is  well  developed,  and  is  rich  in 
vertebrate  remains.  The  strata  rest  uncon  form  ably  on  the 
Miocene,  and  there  is  a  well  marked  faunal  change  at  this 
point,  modern  types  now  first  making  their  appearance.  For 
these  reasons,  we  are  justified  in  separating  the  Miocene  from 
the  Pliocene  at  this  break;  although  in  Europe  where  no 
marked  break  exists,  the  line  seems  to  have  been  drawn  at  a 
somewhat  higher  horizon.  Our  Pliocene  forms  essentially  a 
continuous  series,  although  the  upper  beds  may  be  distin- 
guished from  the  lower  by  the  presence  of  a  true  Equus,  and 
some  other  existing  genera.  The  Pliocene  climate  was  similar  to 
that  of  the  Miocene.  The  Post-Pliocene  beds  contain  many  ex- 
tinct mammals,  and  may  thus  be  separated  from  recent  deposits. 

Eeturning  now  to  our  subject  from  this  geological  digression, 
— which  will  hardly  be  deemed  unprofitable,  since  I  have  given 
you  in  few  words  the  results  of  a  great  deal  of  hard  mountain 
work, — let  us  consider  the  Tertiary  mammals,  as  we  know 
them  from  the  remains  already  discovered,  and  attempt  to 
trace  the  history  of  each  order  down  to  the  present  time.  We 
have  seen  that  a  single  small  Marsupial,  from  the  Trias,  is 
the  only  mammal  found  in  all  the  American  rocks  below  the 
Eocene;  and  yet  in  beds  of  this  age,  immediately  over  the 
Chalk,  fossil  mammals  of  many  different  kinds'  abound. 

The  Marsupials,  strange  to  say,  are  here  few  in  number,  and 
diminutive  in  size;  and  have  as  yet  been  identified  only  by  frag- 


27 

mentary  specimens,  and  most  of  them  too  imperfect  for  accurate 
description.  In  the  higher  Eocene  deposits,  this  group  is  more 
abundant,  but  still  represented  by  small  animals,  most  of  them 
insectivorous,  or  carnivorous  in  habit,  like  the  existing  Opos- 
sum. From  the  Miocene  and  Pliocene,  no  remains  of  Marsupials 
have  been  described.  From  the  Post-Tertiary,  only  specimens 
nearly  allied  to  those  now  living  are  known,  and  most  of  these 
were  found  in  the  caves  of  South  America. 

The  Edentate  Mammals  are  evidently  an  American  type, 
and  on  this  Continent  attained  a  great  development  in  numbers 
and  size.  No  Eocene  Edentates  have  been  found  here,  and 
although  their  discovery  in  this  formation  has  been  announced, 
the  identification  proves  to  have  been  erroneous.  In  the  Mio- 
cene of  the  Pacific  Coast,  a  few  fossils  have  been  discovered 
which  belong  to  animals  of  this  group,  and  to  the  genus  Moropus. 
There  are  two  species,  one  about  as  large  as  a  Tapir,  and  the 
other  nearly  twice  that  size.  This  genus  is  the  type  of  a  dis- 
tinct family,  the  Moropodidce.  In  the  lower  Pliocene  above, 
well  preserved  remains  of  Edentates  of  very  large  size  have 
been  found  at  several  widely  separated  localities  in  Idaho  and 
California.  These  belong  to  the  genus  Morotherium,  of  which 
two  species  are  known.  East  of  the  Eocky  Mountains,  in  the 
lower  Pliocene  of  Nebraska,  a  large  species  apparently  of  the 
genus  Moropus  has  been  discovered.  The  horizon  of  these 
later  fossils  corresponds  nearly  with  beds  in  Europe  that  have 
been  called  Miocene.  In  the  Post-Pliocene  of  North  America, 
gigantic  Edentates  were  very  numerous  and  widely  distributed, 
but  all  disappeared  with  the  close  of  that  period.  These  forms 
were  essentially  huge  Sloths,  and  the  more  important  genera 
were  Megatherium,  Mylodon  and  Megalonyx.  The  genera 
Megalocnus  and  Myomorphus  have  been  found  only  in  Cuba. 

In  South  America  during  the  Pliocene  or  Post-Pliocene, 
enormous  Edentates  were  still  more  abundant,  and  their 
remains  are  usually  in  such  perfect  preservation  as  to  suggest 
a  very  recent  period  for  their  extinction.  The  Sloth  tribe 
is  represented  by  the  huge  Mylodon,  Megatherium,  Megalonyx, 


28 

Coelodon,  Ochotheriutn,  Gnathopis,  Lestodon,  Scelidotherium,  and 
SphcBnodon ;  and  among  the  Armadilloes  were  Chlainydotherium, 
Eurydon,  Glyptodon,  fleterodon,  Pachytherium  and  Schistopleurum. 
Glossotherium,  another  extinct  gen  as,  is  supposed  to  be  allied 
to  the  Ant-eaters. 

It  is  frequently  asserted,  and  very  generally  believed,  that  the 
large  number  of  huge  Edentata  which  lived  in  North  America 
during  the  Post-Pliocene,  were  the  results  of  an  extensive 
migration  from  South  America  soon  after  the  elevation  of 
the  Isthmus  of  Panama,  near  the  close  of  the  Tertiary.  No 
conclusive  proof  of  such  migration  has  been  offered,  and 
the  evidence,  it  seems  to  me,  so  far  as  we  now  have  it,  is 
directly  opposed  to  this  view.  No  undoubted  Tertiary  Edentates 
have  _yet  been  discovered  in  South  America,  while  we  have  at 
least  two  species  in  our  Miocene,  and  during  the  deposition  of 
our  lower  Pliocene,  large  individuals  of  this  group  were  not 
uncommon  as  far  north  as  the  forty-third  parallel  of  latitude, 
on  both  sides  of  the  Rocky  Mountains.  In  view  of  these  facts, 
and  others  which  I  shall  lay  before  you,  it  seems  more  natural 
to  conclude  from  our  present  knowledge,  that  the  migration, 
which  no  doubt  took  place,  was  from  north  to  south.  The 
Edentates  finding  thus  in  South  America  a  congenial  home 
flourished  greatly  for  a  time,  and  although  the  larger  forms  are 
now  all  extinct,  diminutive  representatives  of  the  group  still 
inhabit  the  same  region. 

The  Cetacea  first  appear  in  the  Eocene,  as  in  Europe,  and 
are  comparatively  abundant  in  deposits  of  this  age  on  the 
Atlantic  Coast.  The  most  interesting  remains  of  this  order,  yet 
found,  belong  to  the  Zeuglodontidw,  which  are  carnivorous 
whales,  and  the  only  animals  of  the  order  with  teeth  implanted 
by  two  roots.  The  principal  genera  of  this  family  are  Zeuglodon 
and  Squalodon,  the  former  genus  being  represented  by  gigantic 
forms,  some  of  which  were  seventy  feet  in  length.  The  genus 
Saurocetes,  which  includes  some  small  animals  of  this  group,  has 
been  found  in  South  America.  The  Dolphin  family  (Delphini- 
dce)  are  well  .represented  in  the  Miocene,  both  on  the  Atlantic 


29 

and  Pacific  Coast,  The  best  known  genus  is  Priscodelphinus,  of 
which  several  species  have  been  described.  Several  other 
generic  names  which  have  been  applied  to  fragments  need  not 
here  be  enumerated.  In  none  of  the  Tertiary  species  of  this 
family  were  the  cervical  vertebrae  ankylosed.  The  Sperm 
Whales  (Catodontidce)  were  also  abundant  throughout  the  Ter- 
tiary, and  with  them  in  the  earlier  beds,  various  Ziphioid  forms 
have  been  found.  The  toothless  Bakenidce  are  only  known 
with  certainty  as  fossils  from  the  later  Tertiary  and  more 
recent  deposits. 

The  Sirenians,  which  appear  first  in  the  Eocene  of  the 
Old  World,  occur  in  the  Miocene  of  our.  Eastern  Coast,  and 
throughout  the  later  Tertiary.  The  specimens  described  have 
ail  been  referred  to  the  genus  Manatus,  and  seem  closely 
related  to  our  living  species.  In  the  Tertiary  of  Jamaica,  a 
skull  has  been  found  which  indicates  a  new  genus,  Prorastomus, 
also  allied  to  the  existing  Manatee.  The  genus  Rhytina,  once 
abundant  on  our  Northwest  Coast,  has  recently  become  extinct. 

The  Ungulates  are  the  most  abundant  Mammals  in  the  Ter- 
tiary, and  the  most  important;  since  they  include  a  great 
variety  of  types,  some  of  which  we  can  trace  through  their 
various  changes  down  to  the  modified  forms  that  represent 
them  to-day.  Of  the  various  divisions  in  this  comprehensive 
group,  the  Perissodactyle,  or  odd-toed  Ungulates,  are  evidently 
the  oldest,  and  throughout  the  Eocene  are  the  prevailing  forms. 
Although  all  of  the  Perissodactyles  of  the  earlier  Tertiary  are 
more  or  less  generalized,  they  are  still  quite  distinct  from  the 
Artiodactyles,  even  at  the  base  of  the  Eocene.  One 
family,  however,  the  CoryphodontidoB,  which  is  well  represented 
at  this  horizon,  both  in  America  and  Europe,  although  essen- 
tially Periseodactyle,  possesses  some  characters  which  point  to  a 
primitive  Ungulate  type  from  which  the  present  orders  have 
been  evolved.  Among  these  characters  are  the  diminutive 
brain,  which  in  size  and  form  approaches  that  of  the  Reptiles, 
and  also  the  five-toed  feet  from  which  all  the  various  forms  of 
the  mammalian  foot  have  been  derived.  Of  this  family,  only 


30 

a  single  genus,  Ooryphodon  (Bathmodori),  is  known,  but  there 
were  several  distinct  species.  They  were  the  largest  mammals 
of  the  lower  Eocene,  some  exceeding  in  size  the  existing  Tapirs. 

In  the  middle  Eocene,  West  of  the  Kocky  Mountains,  a 
remarkable  group  of  ungulates  makes  its  appearance.  These 
animals  nearly  equaled  the  Elephant  in  size,  but  had  shorter 
limbs.  The  skull  was  armed  with  two  or  three  pairs  of  horn- 
cores,  and  with  enormous  canine  tusks.  The  brain  was  propor- 
tionally smaller  than  in  any  other  land  mammal.  The  feet  had 
five  toes,  and  resembled  in  their  general  structure  those  of  Co- 
ryphodon,  thus  indicating  some  affinity  with  that  genus.  These 
mammals  resemble  in  some  respects  the  Perissodactyles,  and  in 
others  the  Proboscidians,  yet  differ  so  widely  from  any  known 
Ungulates,  recent  or  fossil,  that  they  must  be  regarded  as  form- 
ing a  distinct  order,  the  Dinocerata.  Only  three  genera  are 
known,  Dinoceras,  Tinoceras  and  Umtatherium,  but  quite  a  num- 
ber of  species  have  been  described.  During  the  later  part  of  the 
middle  Eocene,  these  animals  were  very  abundant  for  a  short 
time,  and  then  became  extinct,  leaving  apparently  no  succes- 
sors, unless  possibly  we  have  in  the  Proboscidians  their  much 
modified  descendants.  Their  genetic  connection  with  the 
Coryphodonts  is  much  more  probable,  in  view  of  what  we 
now  know  of  the  two  groups. 

Besides  these  peculiar  Mammals,  which  are  extinct,  and 
mainly  of  interest  to  the  Biologist,  there  were  others  in  the 
early  Tertiary  which  remind  us  of  those  at  present  living 
around  us.  When  a  student  in  Germany  some  twelve  years 
ago,  I  heard  a  world-renowned  Professor  of  Zoology  gravely 
inform  his  pupils  that  the  Horse  was  a  gift  of  the  Old  World 
to  the  New,  and  was  entirely  unknown  in  America  until 
introduced  by  the  Spaniards.  After  the  lecture,  I  asked  him 
whether  no  earlier  remains  of  horses  had  been  found  on 
this  Continent,  and  was  told  in  reply  that  the  reports  to  that 
effect  were  too  unsatisfactory  to  be  presented  as  facts  in  science. 
This  remark  led  me,  on  my  return,  to  examine  the  subject 
myself,  and  I  have  since  unearthed,  with  my  own  hands,  not  less 


31 

than  thirty  distinct  species  of  the  horse  tribe,  in  the  Tertiary 
deposits  of  the  West  alone ;  and  it  is  now,  I  think  generally 
admitted  that  America  is,  after  all,  the  true  home  of  the  Horse. 

I  can  offer  you  no  better  illustration  than  this  of  the  advance 
vertebrate  palaeontology  has  made  during  the  last  decade,  or  of 
the  important  contributions  to  this  progress  which  our  Rocky 
Mountain  region  has  supplied. 

The  oldest  representative  of  the  horse,  at  present  known,  is 
the  diminutive  Eohippus  from  the  lower  Eocene.  Several  spe- 
cies have  been  found,  all  about  the  size  of  a  fox.  Like  most 
of  the  early  mammals,  these  Ungulates  had  forty-four  teeth, 
the  molars  with  short  crowns,  and  quite  distinct  in  form  from 
the  premolars.  The  ulna  and  the  fibula  were  entire  and  dis- 
tinct, and  there  were  four  well  developed  toes  and  a  rudiment 
of  another  on  the  fore  feet,  and  three  toes  behind.  In  the 
structure  of  the  feet,  and  in  the  teeth,  the  Eohippus  indicates 
unmistakably  that  the  direct  ancestral  line  to  the  modern  horse 
has  already  separated  from  the  other  Perissodactyles.  In  the 
next  higher  division  of  the  Eocene,  another  genus  (Orohippus) 
makes  its  appearance,  replacing  Eohippus,  and  showing  a 
greater,  although  still  distant,  resemblance  to  the  Equine  type. 
The  rudimentary  first  digit  of  the  fore  foot  has  disappeared, 
and  the  last  premolar  has  gone  over  to  the  molar  series.  Oro- 
hippus was  but  little  larger  than  Eohippus,  and  in  most  other 
respects  very  similar.  Several  species  have  been  found  in  the 
same  horizon  with  Dinoceras,  and  others  lived  during  the  upper 
Eocene  with  Diplacodon,  but  none  later. 

Near  the  base  of  the  Miocene,  in  the  Brontotherium  beds, 
we  find  a  third  closely  allied  genus,  Mesoliippus,  which  is  about 
as  large  as  a  sheep,  and  one  stage  nearer  the  horse.  There  are 
only  three  toes  and  a  rudimentary  splint  bone  on  the  fore  feet, 
and  three  toes  behind.  Two  of  the  premolar  teeth  are  quite 
like  the  molars.  The  ulna  is  no  longer  distinct,  or  the  fibula 
entire,  and  other  characters  show  clearly  that  the  transition  is 
advancing.  In  the  upper  Miocene,  Mesohippus  is  not  found, 
but  in  its  place  a  fourth  form,  Miohippus,  continues  the  line. 


32 

This  genus  is  near  the  Anchitherium  of  Europe,  but  presents 
several  important  differences.  The  three  toes  in  each  foot  are 
more  nearly  of  a  size,  and  a  rudiment  of  the  fifth  metacarpal 
bone  is  retained.  All  the  known  species  of  this  genus  are  larger 
than  those  of  Mesohippus,  and  none  pass  above  the  Miocene. 

The  genus  Protohippus  of  the  lower  Pliocene,  is  yet  more 
equine,  and  some  of  its  species  equaled  the  ass  in  size.  There 
are  still  three  toes  on  each  foot,  but  only  the  middle  one,  cor: 
responding  to  the  single  toe  of  the  horse,  comes  to  the  ground. 
This  genus  resembles  most  nearly  the  Hipparion  of  Europe. 
In  the  Pliocene,  we  have  the  last  stage  of  the  series  before 
reaching  the  horse,  in  the  genus  Pliohippus,  which  has  lost  the 
small  hooflets,  and  in  other  respects  is  very  equine.  Only  in 
the  upper  Pliocene,  does  the  true  Equus  appear,  and  complete 
the  genealogy  of  the  Horse,  which  in  the  Post-Tertiary  roamed 
over  the  whole  of  North  and  South  America,  and  soon  after 
became  extinct.  This  occurred  long  before  the  discovery  of 
the  Continent  by  Europeans,  and  no  satisfactory  reason  for  the 
extinction  has  yet  been  given.  Besides  the  characters  I  have 
mentioned,  there  are  many  others,  in  the  skeleton,  skull,  teeth, 
and  brain  of  the  forty  or  more  intermediate  species,  .which 
show  that  the  transition  from  the  Eocene  Eoliippus  to  the 
modern  Equus,  has  taken  place  in  the  order  indicated,  and  I 
believe  the  specimens  now  at  New  Haven  will  demonstrate 
the  fact  to  any  anatomist.  They  certainly  carried  prompt 
conviction  to  the  first  of  anatomists,  who  was  the  honored  guest 
of  the  Association  a  year  ago,  whose  genius  had  already  indi- 
cated the  later  genealogy  of  the  horse  in  Europe,  and  whose 
own  researches  so  well  qualified  him  to  appreciate  the  evidence 
here  laid  before  him.  Did  time  permit,  I  might  give  you  at 
least  a  probable  explanation  of  this  marvellous  change,  but 
justice  to  the  comrades  of  the  horse  in  his  long  struggle  for 
existence  demands  that  some  notice  of  their  efforts  should  be 
placed  on  record. 

Beside  the  Horse  and  his  congeners,  the  only  existing  Peris- 
sodactyles  are  the  Rhinoceros  and  the  Tapir.  The  last  is  the 


33 

oldest  type,  but  the  Rhinoceros  bad  near  allies  throughout  the 
Tertiary  ;  and,  in  view  of  the  continuity  of  the  equine  line,  it  is 
well  worth  while  to  attempt  to  trace  his  pedigree.  At  the 
bottom  of  the  Eocene,  in  our  Western  lake-basins,  the  tapiroid 
genus  Helaletes  is  found,  represented  by  numerous  small  mam- 
mals hardly  larger  than  the  diminutive  horses  of  that  day.  In 
the  following  epoch  of  the  Eocene,  the  closely  allied  Ilyracliyus 
was  one  of  the  most  abundant  animals.  This  genus  was  nearly 
related  to  the  Lophiodon  of  Europe,  and  in  its  teeth  and  skele- 
ton strongly  resembled  the  living  Tapir ;  whose  ancestry,  to 
this  point,  seems  to  coincide  with  that  of  the  Rhinoceros  we 
are  considering.  Strangely  enough,  the  Rhinoceros  line,  before 
it  becomes  distinct,  separates  into  two  branches.  In  the  upper 
part  of  the  Dinoceras  Beds,  we  have  the  genus  Colonoceras, 
which  is  really  a  Hyrachyus  with  a  transverse  pair  of  very 
rudimentary  horn-cores  on  the  nasal  bones.  In  the  lower 
Miocene  west  of  the  Rocky  Mountains,  this  line  seems  to  pass 
on  through  the  genus  Dicer atfierium,  and  in  the  higher  Miocene 
this  genus  is  well  represented.  Some  of  the  species  nearly 
equaled  in  size  the  existing  Rhinoceros,  which  Diceraikerium 
strongly  resembled.  The  main  difference  between  them  is  a 
most  interesting  one.  The  rudimentary  horn-cores  on  the 
nasals,  seen  in  Colonoceras,  are  in  Diceratherium  developed  into 
strong  bony  supports  for  horns,  which  were  placed  transversely, 
as  in  the  Ruminants,  and  not  on  the  median  line,  as  in  all 
existing  forms  of  Rhinoceros.  In  the  Pliocene  of  the  Pacific 
Coast,  a  large  Rhinoceros  has  been  discovered,  which  may 
be  a  descendant  of  Diceratherium,  but  as  the  nasal  bones  have 
not  been  found,  we  must  wait  for  further  evidence  on  this 
point.  Returning  now  to  the  other  branch  of  the  Rhinoceros 
group,  which  left  their  remains  mainly  East  of  the  Rocky 
Mountains,  we  find  that  all  the  known  forms  are  hornless. 
The  upper  Eocene  genus  Amynodon  is  the  oldest  known 
Rhinoceros,  and  by  far  the  most  generalized  of  the  family. 
The  premolars  are  all  unlike  the  molars,  the  four  canines  are 
of  large  size,  but  the  inner  incisor  in  each  jaw  is  lost  in  the 
5 


34 

fully  adult  animal.  The  nasals  were  without  horns.  There 
were  four  toes  in  front,  and  three  behind.  The  genus  Hyrac- 
odon,  of  the  Miocene,  which  is  essentially  a  Rhinoceros,  has 
a  full  set  of  incisor  and  canine  teeth;  and  the  molars  are  so 
nearly  like  those  of  its  predecessor  Hyrachyus,  that  no  one  will 
question  the  transformation  of  the  older  into  the  newer  type. 
Hyracodon,  however,  appears  to  be  off  the  true  line,  for  it  has 
but  three  toes  in  front.  In  the  higher  Miocene  beds,  arid 
possibly  with  Hyracodon,  occurs  a  larger  Rhinoceros,  which 
has  been  referred  to  the  genus  Aceratherium.  This  form  has 
lost  the  canine  and  one  incisor  above,  and  two  incisors  below. 
In  the  Pliocene  are  several  species  closely  related,  and  of  large 
size.  Above  the  Pliocene  in  America,  no  vestiges  of  the 
Rhinoceros  have  been  found,  and  our  American  forms  doubt- 
less became  extinct  at  the  close  of  this  period. 

The  Tapir  is  clearly  an  old  American  type,  and  we  have 
seen  that,  in  the  Eocene,  the  genera  Helaletes  and  Hyrachyus 
were  so  strongly  tapiroid  in  their  principal  characters,  that  the 
main  line  of  descent  probably  passed  through  them.  It  is 
remarkable  that  the  Miocene  of  the  West,  so  greatly  developed  as 
it  is  on  both  sides  of  the  Rocky  Mountains,  should  have-yielded 
but  a  few  fragments  of  tapiroid  mammals,  and  the  same  is  true 
of  the  Pliocene  of  that  region.  In  the  Miocene  of  the  Atlantic 
Coast,  too,  only  a  few  imperfect  specimens  have  been  found. 
These  forms  all  apparently  belong  to  the  genus  Tapiravus, 
although  most  of  them  have  been  referred  to  Lophiodon,  a  lower 
Eocene  type.  In  the  Post-Tertiary,  a  true  Tapirus  was  abun- 
dant, and  its  remains  have  been  found  in  various  parts  of  North 
America.  The  line  of  descent,  although  indistinct  through 
the  middle  and  upper  Tertiary,  was  doubtless  continuous  in 
America,  and  several  species  exist  at  present,  from  Mexico 
southward.  It  is  worthy  of  notice  that  the  species  North  of 
the  Isthmus  of  Panama  appear  all  to  be  generically  distinct 
from  those  of  South  America. 

In  addition  to  these  three  Perissodactyle  types  which,  as 
the  fittest,  have  alone  survived,  and  whose  lineage  I  have 


35 

endeavored  to  trace,  there  were  many  others  in  earl}'  Tertiary 
times.  Some  of  these  disappeared  with  the  close  of  the 
Eocene,  while  others  continued,  and  assumed  strange  special- 
ized shapes  in  the  Miocene,  before  their  decline  and  extinction. 
One  series  of  the  latter  deserves  especial  mention,  as  it  includes 
one  of  the  most  interesting  families  of  our  extinct  animals. 
Among  the  large  mammals  in  the  lower  Eocene  is  Limnohyus, 
a  true  Perissodactyle,  but  only  known  here  from  fragments  of 
the  skeleton.  In  the  next  higher  beds,  this  genus  is  well 
represented,  and  with  it  is  found  a  nearly  allied  form,  Palceo- 
syops.  In  the  upper  Eocene,  both  have  left  the  field,  and  the 
genus  Diplacodon,  a  very  near  relative,  holds  the  supremacy. 
The  line  seems  clear  through  these  three  genera,  but  on 
crossing  the  break'  into  the  Miocene,  we  have,  apparently  as 
next  of  kin,  the  huge  Brontotheridce.  These  strange  beasts  show 
in  their  dentition  and  some  other  characters  the  same  transition 
steps  beyond  Diplacodon,  which  that  genus  had  made  beyond 
Palceosyops.  The  Brontotheridce  were  nearly  as  large  as  the 
Elephant,  but  had  much  shoTter  limbs.  The  skull  was  elon- 
gated, and  had  a  transverse  pair  of  large  horn-cores  on  the 
rnaxillaries,  in  front  of  the  orbits,  like  the  middle  pair  in 
Dinoeeras.  There  were  four  toes  in  front,  and  three  behind, 
and  the  feet  were  similar  to  those  of  the  Rhinoceros.  There 
are  four  genera  in  this  group,  Brontotherium ;  Diconodon;  Afeno- 
dus  (Titanotherium)  ;  and  Megacerops,  which  have  been  found 
only  in  the  lowest  Miocene,  east  of  the  Rocky  Mountains. 

In  the  higher  Miocene  beds  of  Oregon,  an  allied  genus, 
Chalicotherium,  makes  its  appearance.  It  is  one  stage  further 
on  in  the  transition,  and  perhaps  a  descendant  of  the  Bronto- 
theridce ;  but  here,  so  far  as  now  known,  the  line  disappears. 
It  is  a  suo-gestive  fact,  that  this  genus  has  now  been  found  in 

CO  O 

Western  America,  China,  India,  Greece,  Germany  and  France, 
indicating  thus,  as  I  believe,  the  path  by  which  many  of  our 
ancient  mammals  helped  to  people  the  so-called  Old  World. 

The  Artiodactyles,  or  even-toed  Ungulates,  are  the  most 
abundant  of  the  larger  mammals  now  living;  and  the  group 


36 

dates  back  at  least  to  the  lowest  Eocene.  Of  the  two  well 
marked  divisions  of  this  order,  the  Bunodonts  and  the  Seleno- 
donts,  as  happily  defined  by  Kowalevsky,  the  former  is  the 
older  type,  which  must  have  separated  from  the  Perissodactyle 
line  after  the  latter  had  become  differentiated  from  the  prim- 
itive Ungulate.  In  the  Coryphodon  Beds  of  New  Mexico, 
occurs  the  oldest  Artiodactyle  yet  found,  but  it  is  at  present 
known  only  from  fragmentary  specimens.  These  remains  are 
clearly  Suilline  in  character,  and  belong  to  the  genus  EoJiyus. 
In  the  beds  above,  and  possibly  even  in  the  same  horizon, 
the  genus  Helohyus  is  not  uncommon,  and  several  species  are 
known.  The  molar  teeth  of  this  genus  are  very  similar  to 
those  of  the  Eocene  Hyracotherium,  of  Europe,  which  is  sup- 
posed to  be  a  Perissodactyle,  while  Helohyus  certainly  is  not, 
but  apparently  a  true  lineal  ancestor  of  the  existing  pigs. 
In  every  vigorous  primitive  type  which  was  destined  to  survive 
many  geological  changes,  there  seems  to  have  been  a  tendency 
to  throw  off  lateral  branches,  which  became  highly  specialized 
and  soon  died  out,  because  they  are  unable  to  adapt  themselves 
to  new  conditions.  The  narrow  path  of  the  persistent  Suilline 
type,  throughout  the  whole  Tertiary,  is  strown  with  the  remains 
of  such  ambitious  offshoots,  while  the  typical  pig,  with  an 
obstinacy  never  lost,  has  held  on  in  spite  of  Catastrophes  and 
Evolution,  and  still  lives  in  America  to-day.  In  the  lower 
Eocene,  we  have  in  the  genus  Parahyus  apparently  one  of  these 
short-lived,  specialized  branches.  It  attained  a  much  larger 
size  than  the  true  lineal  forms,  and  the  number  of  its  teeth 
was  reduced.  In  the  Dinoceras  Beds,  or  middle  Eocene,  we 
have  still,  on  or  near  the  true  line,  Hdohyus,  which  is  the 
last  of  the  series  known  from  the  American  Eocene.  All 
these  early  Suillines,  with  the  possible  exception  of  Parahyus, 
appear  to  have  had  at  least  four  toes,  all  of  usable  size. 

In  the  lower  Miocene,  we  find  the  genus  Perchoerus,  seem- 
ingly a  true  Suilline,  and  with  it  remains  of  a  larger  form, 
Elotherium,  are  abundant.  The  latter  genus  occurs  in  Europe 
in  nearly., the  same  horizon,  and  the  specimens  known  from 


37 

each  Continent  agree  closely  in  general  characters.  The  name 
Pelonax  has  been  applied  erroneously  to  some  of  the  American 
forms  ;  but  the  specimens  on  which  it  was  based  clearly  belong 
to  Elotherium.  This  genus  affords  another  example  of  the 
aberrant  Suilline  offshoots,  already  mentioned.  Some  of  the 
species  were  nearly  as  large  as  a  Rhinoceros,  and  in  all  there  were 
but  two  serviceable  toes;  the  outer  digits,  seen  in  living  ani- 
mals of  this  group,  being  represented  only  by  small  rudiments 
concealed  beneath  the  skin.  In  the  upper  Miocene  of  Oregon, 
Suillines  are  abundant,  and  almost  all  belong  to  the  genus 
Thinohyus,  a  near  ally  of  the  modern  Peccary  (Dicotyles),  but 
having  a  greater  number  of  teeth,  and  a  few  other  distinguish- 
ing features.  In  the  Pliocene,  Suillines  are  still  numerous,  and 
all  the  American  forms  yet  discovered  are  closely  related  to 
Dicotyles.  The  genus  Platygonus  is  represented  by  several 
species,  one  of  which  was  very  abundant  in  the  Post-Tertiary 
of  North  America,  and  is  apparently  the  last  example  of  a  side 
branch,  before  the  American  Suillines  culminate  in  existing 
Peccaries.  The  feet  in  this'  species  are  more  specialized  than 
in  the  living  forms,  and  approach  some  of  the  peculiar  features 
of  the  ruminants ;  as  for  example  a  strong  tendency  to  coales- 
cence in  the  meta  podia!  bones.  The  genus  Platygonus  became 
extinct  in  the  Post- Tertiary,  and  the  later  and  existing  species 
are  all  true  Peccaries.  No  authenticated  remains  of  the  genera 
Sus,  Porous,  Phacochcerus,  or  the  allied  Hippopotamus,  the  Old 
World  Suillines,  have  been  found  in  America,  although  several 
announcements  to  that  effect  have  been  made. 

In  the  series  of  generic  forms  between  the  lower  Eocene 
Eohyus  and  the  existing  Dicotyles.  which  I  have  very  briefly 
discussed,  we  have  apparently  the  ancestral  line  ending  in  the 
typical  American  Suillines.  Although  the  demonstration  is 
not  yet  as  complete  as  in  the  lineage  of  the  Horse,  this  is  not 
owing  to  want  of  material,  but  rather  to  the  fact  that  the 
actual  changes  which  transformed  the  early  Tertiary  pig  into 
the  modern  Peccary  were  comparatively  slight,  so  far  as  they 
are  indicated  in  the  skeletons  preserved,  while  the  lateral 


38 

branches  were  so  numerous  as  to  confuse  the  line.  It  is  clear, 
however,  that  from  the  close  of  the  Cretaceous  to  the  Post- 
Tertiary,  the  Bunodont  Artiodactyles  were  especially  abun- 
dant on  this  Continent,  and  only  recently  have  approached 
extinction. 

The  Selenodont  division  of  the  Artiodactyles  is  a  more 
interesting  group  and,  so  far  as  we  now  know,  makes  its  first 
appearance  in  the  upper  Eocene  of  the  West,  although  forms, - 
apparently  transitional,  between  it  and  the  Bunodonts  occur  in 
the  Dinoceras  Beds,  or  middle  Eocene.  These  belong  to  the 
genus  Homacodon,  which  is  very  nearly  allied  to  Ilelohyus  and 
but  a  single  step  away  from  this  genus  toward  the  Selenodonts. 
By  a  fortunate  discovery,  a  nearly  complete  skeleton  of  this 
rare  intermediate  form  has  been  brought  to  light,  and  we  are 
thus  enabled  to  define  its  characters.  Several  species  of 
Homacodon  are  known,  all  of  small  size.  This  primitive 
Selenodont  had  forty-four  teeth,  which  formed  a  nearly  con- 
tinuous series. 

The  molar  teeth  are  very  similar  to  those  of  ffelohyus,  but 
the  cones  on  the  crowns  have  become  partially  triangular  in 
outline,  so  that  when  worn,  the  Selenodont  pattern  is  clearly 
recognizable.  The  first  and  second  upper  molars,  moreover, 
have  three  distinct  posterior  cusps,  and  two  in  front;  a  peculiar 
feature,  which  is  seen  also  in  the  European  genera  Dichobune 
and  Cainotherium.  There  were  four  toes  on  each  foot,  and  the 
metapodial  bones  were  distinct.  The  type  species  of  this  genus 
was  about  as  large  as  a  cat.  With  Helohyus,  this  genus  forms 
a  well  marked  family,  the  Helohyidw. 

In  the  Diplacodon  horizon  of  the  upper  Eocene,  the  Seleno- 
dont dentition  is  no  longer  doubtful,  as  it  is  seen  in  most  of 
the  Artiodactyla  yet  found  in  these  beds.  These  animals  are 
all  small,  and  belong  to  at  least  three  distinct  genera.  One  of 
these,  Eomeryx,  closely  resembles  Homacodon  in  most  of  its 
skeleton,  and  has  four  toes,  but  its  teeth  show  well  marked 
crescents,  and  a  partial  transition  to  the  teeth  of  Hyopolamus, 
from  the  Eocene  of  Europe.  With  this  genus,  is  another 


39 

(Parameryx),  also  closely  allied  to  Homacodon,  but  apparently  a 
straggler  from  the  true  line,  as  it  has  but  three  toes  behind. 
The  most  pronounced  Selenodont  in  the  upper  Eocene  is  the 
Oromeryx,  which  genus  -appears  to  be  allied  to  the  existing 
Deer  family,  or  Cervidce,  and  if  so  is  the  oldest  known  repre- 
sentative of  the  group.  These  facts  are  important,  as  it  has 
been  supposed,  until  very  recently,  that  our  Eocene  contained 
no  even-hoofed  mammals. 

In  -the  lowest  Miocene  of  the  West,  no  true  crescent-toothed 
Arliodactyla  have  as  yet  been  identified,  with  the  exception 
of  a  single  species  of  Hyopoiamus  ;  but  in  the  overlying  beds 
of  the  middle  Miocene,  remains  of  the  Oreodoniidw  occur  in 
such  vast  numbers  as  to  indicate  that  these  animals  must 
have  lived  in  large  herds  around  the  borders  of  the  lake-basins 
in  which  their  remains  have  been  entombed.  These  basins  are 
now  the  denuded  deserts  so  well  termed  Mauvaises  Terres  by 
the  early  French  trappers.  The  least  specialized,  and  apparently 
the  oldest,  genus  of  this  group  is  Agriochcerus,  which  so  nearly 
resembles  the  older  Plyopotdmus,  and  the  still  more  ancient 
Eomeryx,  that  we  can  hardly  doubt  that  they  all  belonged  to 
the  same  ancestral  line.  The  typical  Oreodonts  are  the  genera 
Oreodon  and  Eporeodon,  which  have  been  aptly  termed  by 
Leidy,  ruminating  hogs.  They  had  forty-four  teeth,  and  four 
well  developed  toes  on  each  foot.  The  true  Oreodons,  which 
were  most  numerous  east  of  the  Rocky  Mountains,  were  about 
as  large  as  the  existing  Peccary,  while  Eporeodon,  which  was 
nearly  twice  this  size,  was  very  abundant  in  the  Miocene  of 
the  Pacific  slope. 

In  the  succeeding  Pliocene  formation,  on  each  side  of  the 
Rocky  Mountains,  the  genus  Merychyus  is  one  of  the  prevailing 
forms,  and  continues  the  line  on  from  the  Miocene,  where  the 
true  Oreodons  became  extinct.  Beyond  this,  we  have  the  genus 
Merychochmrus,  which  is  so  nearly  allied  to  the  last,  that  they 
would  be  united  by  many  naturalists.  With  the  close  of  the 
Pliocene,  this  series  of  peculiar  ruminants  abruptly  terminates, 
no  member  surviving  until  the  Post-Tertiary,  so  far  as  known. 


•        40 

A  most  interesting  line,  that  leading  to  the  Camels  and  Lla- 
mas, separates  from  the  primitive  Selenodont  branch  in  the 
Eocene,  probably  through  the  genus  Parameryx.  In  the  Mio- 
cene, we  find  in  Poebrotherium  and  some  nearly  allied  forms 
unmistakable  indications  that  the  Cameloid  type  of  ruminant 
had  already  become  partially  specialized,  although  there  is  a 
complete  series  of  incisor  teeth,  and  the  metapodial  bones  are 
distinct.  In  the  Pliocene,  the  Camel  tribe  was,  next  to  the 
Horses,  the  most  abundant  of  the  larger  mammals.  The  line  is 
continued  through  the  genus  Procamelus,  and  perhaps  others, 
and  in  this  formation  the  incisors  first  begin  to  diminish,  and 
the  metapodials  to  unite.  In  the  Post-Tertiary  we  have  a  true 
Auchenia,  represented  by  several  species,  and  others  in  South 
America,  where  the  Alpacas  and  Llamas  still  survive.  From 
the  Eocene  almost  to  the  present  time,  North  America  has  been 
the  home  of  vast  numbers  of  the  Camelidce,  and  there  can  be 
little  doubt  that  they  originated  here,  and  migrated  to  the  Old 
World. 

Returning  once  more  to  the  upper  Eocene,  we  find  another 
line  of  descent  starting  from  Oromeryx,  which,  as  we  have 
seen,  had  apparently  then  just  become  differentiated  from  the 
older  Bunodont  type.  Throughout  the  middle  and  upper 
Miocene,  this  line  is  carried  forward  by  the  genus  Leptomeryx 
and  its  near  allies,  which  resemble  so  strongly  the  Pliocene 
Cervidce  that  they  may  fairly  be  regarded  as  their  probable 
progenitors.  Possibly  some  of  these  forms  may  be  related  to 
the  Tragulidce,  but  at  present  the  evidence  is  against  it. 

The  Deer  family  has  representatives  in  the  upper  Miocene  of 
Europe,  which  contains  fossils  strongly  resembling  the  fauna  of 
our  lower  Pliocene,  a  fact  always  to  be  borne  in  mind  in  com- 
paring the  horizon  of  any  group  in  the  two  continents.  Several 
species  of  Cervidce,  belonging  to  the  genus  Cosoryx,  are  known 
from  the  lower  Pliocene  of  the  West,  and  all  have  very  small 
antlers,  divided  into  a  single  pair  of  tynes.  The  statement 
recently  published,  that  most  of  these  antlers  had  been  broken 
during  the. -life  of  the  animals,  is  unsupported  by  any  evidence, 


41 

and  is  erroneous.  These  primitive  Deer  do  not  have  the  orbit 
closed  behind,  and  they  have  all  the  four  metapodial  bones 
entire,  although  the  second  and  fifth  are  very  slender.  In  the 
uppei'  Pliocene,  a  true  C&rvus  of  large  size  has  been  discovered. 
In  the  Post-Tertiary,  Cervus,  Akes,  and  Tarandus  have  been  met 
with,  the  latter  far  south  of  its  present  range.  In  the  caves  of 
South  America,  remains  of  Cervus  have  been  found,  and  also  two 
species  of  Antelopes,  one  referred  to  a  new  genus,  Leptothei  ium. 

The  Hollow-horned  Ruminants,  in  this  country,  appear  to 
date  back  no  further  than  to  the  lower  Pliocene,  and  here  only 
two  species  of  Bid  n  have  as  yet  been  discovered.  In  the  Post- 
Tertiary  this  geniis  was  represented  by  numerous  individuals 
and  several  species,  some  of  large  size.  The  Mask  Ox  (Ouibos) 
was  not  uncommon  during  some  parts  of  this  epoch,  and 
its  remains  are  widely  distributed. 

No  authentic  fossil  remains  of  true  Sheep,  Goats,  or  Giraffes 
have  as  yet  been  found  on  this  continent. 

The  Proboscideans,  which  are  now  separated  from  the  typi- 
cal Ungulates  as  a  distinct  order,  make  their  first  appearance  in 
North  America  in  the  lower  Pliocene,  where  several  species  of 
Mastodon  have  been  found.  This  genus  occurs,  also,  in  the 
upper  Pliocene,  and  in  the  Post-Tertiary;  although  some  of 
the  remains  attributed  to  the  latter  are  undoubtedly  older. 
The  Pliocene  species  all  have  a  band  of  enamel  on  the  tusks, 
and  some  other  peculiarities  observed  in  the  oldest  Mastodons 
of  Europe,  which  are  from  essentially  the  same  horizon.  Two 
species  of  this  genus  have  been  found  in  South  America,  in 
connection  with  the  remains  of  extinct  Llamas  and  Horses. 
The  genus  Elephas  is  a  later  form,  and  has  not  yet  been  iden- 
tified in  this  country  below  the  upper  Pliocene,  where  one 
gigantic  species  was  abundant.  In  the  Post-Pliocene,  remains 
of  this  genus  are  numerous.  The  hairy  Mammoth  of  the  Old 
World  (Elephas  primigenius)  was  once  abundant  in  Alaska,  and 
great  numbers  of  its  bones  are  now  preserved  in  the  frozen 
cliffs  of  that  region.  This  species  does  not  appear  to  have 
extended  east  of  the  Rocky  Mountains,  or  south  of  the  Colum- 
6 


42 

bia  River,  but  was  replaced  there  by  the  American  Elephant, 
which  preferred  a  milder  climate.  Remains  of  the  latter  have 
been  met  with  in  Canada,  throughout  the  United  States,  and  in 
Mexico.  The  last  of  the  American  Mastodons  and  Elephants 
became  extinct  in  the  Post-Tertiary. 

The  order  Toxodontia  includes  two  very  peculiar  genera, 
Toxodon  and  Nesodon,  which  have  been  found  in  the  Post-Ter- 
tiary deposits  of  South  America.  These  animals  were  of  huge- 
size,  and  possessed  such  mixed  characters  that  their  affinities 
are  a  matter  of  considerable  doubt.  They  are  thought  to  be 
related  to  the  Ungulates,  Rodents,  and  Edentates,  but  as  the 
feet  are  unknown,  this  cannot  at  present  be  decided. 

Macrauchenia  and  Homalodontotherium  are  two  other  peculiar 
genera  from  South  America,  now  extinct,  the  exact  affinities 
of  which  are  uncertain.  AnoplotJierium  and  Palceolherium,  so 
abundant  in  Europe,  have  not  been  found  in  our  North 
American  Tertiary  deposits,  although  reported  from  South 
America. 

Perhaps  the  most  remarkable  mammals  yet  found  in  Amer- 
ica are  the  Tillodontia,  which  are  comparatively  abundant  in 
the  lower  and  middle  Eocene.  These  animals  seem  to.  com- 
bine the  characters  of  several  different  groups,  viz :  the  Car- 
nivores, Ungulates,  and  Rodents.  In  the  genus  Tillotherium, 
the  type  of  the  order,  and  of  the  family  Tillotheridce,  the  skull 
resembles  that  of  the  Bears ;  the  molar  teeth  are  of  the 
ungulate  type;  while  the  large  incisors  are  very  similar  to  those 
of  Rodents.  The  skeleton  resembles  that  of  the  Carnivores, 
but  the  scaphoid  and  lunar  bones  are  distinct,  and  there  is  a 
third  trochanter  on  the  femur.  The  feet  are  plantigrade,  and 
each  had  five  digits,  all  with  long  pointed  claws.  In  the 
allied  genus  Stylinodon,  which  belongs  to  a  distinct  family,  the 
StylinodoniidcK,  all  the  teeth  were  rootless.  Some  of  these 
animals  were  as  large  as  a  Tapir.  The  genus  Dryptodon  has 
been  found  only  in  the  Coryphodon  beds  of  New  Mexico,  while 
Tillotherium  and  Stylinodon  occur  in  the  middle  Eocene  of 
Wyoming.  Anchippodus  probably  belongs  to  this  group,  which 


43 

may  perhaps  include  some  other  forms  that  have  been  named 
from  fragmentary  specimens. 

The  Rodents  are  an  ancient  type,  and  their  remains  are  not 
unfrequeutly  disinterred  in  the  strata  of  our  lowest  fresh-water 
Eocene.  The  earliest  known  forms  are  apparently  all  related 
to  the  Squirrels,  and  the  most  common  genus  is  Sciwravus, 
which  continued  throughout  the  Eocene.  A  nearly  allied  form, 
which  may  prove  to  be  the  same,  is  Paramys,  the  species  of 
which  are  larger  than  those  of  the  older  type.  In  the  Dino- 
ceras  beds,  the  genus  Colonomys  is  found,  and  the  specimens 
preserved  point  to  the  Muridce,  as  the  nearest  living  allies.  A 
peculiar  genus,  Apaiemys,  which  also  occurs  in  the  middle 
Eocene,  has  gliriform  incisors,  but  the  molars  resemble  those  of 
Insectivores.  All  the  Eocene  Rodents  are  of  small  size,  the 
largest  being  about  as  large  as  a  rabbit. 

In  the  middle  and  upper  Miocene  lake-basins  of  the  West, 
Rodents  abound,  but  all  are  of  moderate  size.  The  Hares  first 
appear  in  the  Oreodon  beds,  and  continue  in  considerable  num- 
bers through  the  rest  of  the  Tertiary  and  Post-Tertiary  to  the 
present  day.  In  these  beds,  the  most  common  forms  belong  to 
the  Leporidw,  and  mainly  to  the  genus  Palocolagus.  The  Squirrel 
family  is  represented  by  Ischyromys,  the  Muridce  by  the  genus 
Eumys,  and  the  Beavers  by  Palceocastor.  In  the  upper  Miocene 
of  Oregon,  most  of  the  same  genera  are  found,  and  with  them 
some  peculiar  forms,  very  unlike  anything  now  living.  One  of 
these  is  the  genus  Allomys*  possibly  related  to  the  flying 
Squirrels,  but  having  molar  teeth  somewhat  like  those  of  the 
Ungulates.  In  the  Pliocene,  east  and  west  of  the  Rocky  Moun- 
tains, Rodents  continue  abundant,  but  most  of  them  belong  to 
existing  genera.  Among  these  are  Castor,  Hystrioc,  Cynomys, 
Geomys,  Lepus  and  Hesperomys,  In  the  Post-Tertiary,  the 
gigantic  beaver,  Castoroides,  was  abundant  throughout  most  of 
North  America.  Hydrochcerus  has  been  found  in  South  Caro- 
lina. In  the  caves  of  the  island  of  Anguilla,  in  the  West 
Indies,  remains  of  large  extinct  Rodents  belonging  to  the  Chin- 
cliillidce  have  been  discovered. 


44 

The  early  Tertiary  Rodents  known  from  South  America  are 
the  genera  Megamys,  Theridromys,  and  a  large  species  referred 
to  Arvicola.  In  Brazil,  the  Pliocene  Rodents  found  are  referred 
to  the  existing  genera  Cavia,  Kerodon,  Lagostomus,  Ctenomys, 
Hesperomys,  Oxymycterus,  Arvicola  and  Lepus.  A  new  genus, 
Cardiodus,  described  from  this  horizon,  is  a  true  Rodent,  but 
the  peculiar  Typotherium,  which  has  been  referred  to  this  order 
by  some  authorities,  has  perhaps  other  affinities.  In  the' 
Post-Tertiary,  the  Rodents  were  very  abundant  in  South 
America,  as  they  are  at  present.  The  species  are  in  most 
instances  distinct  from  those  now  living,  but  the  genera  are 
nearly  the  same.  The  Caviidae  were  especially  numerous. 
Cercolabes,  Myopolamus,  and  Lagostomus  are  also  found,  and  two 
extinct  genera,  Phyllomys  and  Lonchophorus, 

The  Cheiroptera,  or  Bats,  have  not  been  found  in  this  country 
below  the  middle  Eocene,  where  two  extinct  genera,  Nyctilestes 
and  Nyclitherium,  are  each  represented  by  numerous  remains. 
These  fossils  all  belong  to  small  animals,  and,  so  far  as  they 
have  been  investigated,  show  no  characters  of  more  than  generic 
importance  to  distinguish  them  from  the  Bats  of  to-day.  No 
other  members  of  this  group  are  known  from  our  Tertiary. 
In  the  Post-Tertiary,  no  extinct  species  of  Bats  have  been 
found  in  North  America,  but  from  the  caves  of  Brazil  quite 
a  number  have  been  reported.  These  all  belong  to  genera 
still  living  in  South  America,  and  most  of  them  to  the  family 
Phyllostomidcz. 

The  Insectivores  date  back,  in  this  country,  at  least  to  the 
middle  Eocene.  Here  numerous  remains  occur,  which  have 
been  described  as  belonging  to  this  order,  although  it  is  pos- 
sible that  some  of  them  were  insect-eating  Marsupials.  The 
best  known  genera  are,  Hemiaeodon,  Centetodon,  Talpavus,  and 
Entomacodon ;  all  represented  by  animals  of  small  size.  In 
the  Miocene,  the  bones  of  Insectivores  are  comparatively  abun- 
dant, and  the  genera  best  determined  are  Ictops  and  Leptictis. 
A  few  specimens  only  have  been  found  in  the  Pliocene  and 
Post-Plioeene,  most  of  them  related  to  the  Moles.  No  extinct 


Insectivores  are  known  from  South  America,  and  no  member 
of  the  group  exists  there  at  present. 

The  Carnivora,  or  true  flesh-eating  animals,  are  an  old  type, 
well  represented  in  the  Eocene,  and,  as  might  be  expected, 
these  early  forms  are  much  less  specialized  than  the  living 
species.  In  the  Coryphodon  beds,  the  genus  Limnocyon, 
allied  to  the  Pterodon  of  the  European  Eocene,  is  abundant. 
Another  genus,  apparently  distinct,  is  Prototomus,  and  several 
others  have  been  named  from  fragmentary  fossils.  In  the 
middle  Eocene,  Carnivores  were  still  more  numerous,  and  many 
genera  have  been  discovered.  One  of  these,  Limnofelis,  was 
nearly  as  large  as  a  lion,  and  apparently  allied  to  the  cats, 
although  the  typical  Felidce  seem  not  yet  to  have  been  differen- 
tiated. Another  Carnivore  of  nearly  equal  size  was  Orocyon, 
which  had  short  massive  jaws  and  broad  teeth.  Dromocyon  and 
Mesonyx  were  large  animals,  allied  to  Hycenodon.  The  teeth 
were  narrow,  and  the  jaws  long  and  slender.  Among  the 
smaller  Carnivores  were,  Vulpavus,  Viverravus,  Sinopa,  Thino- 
cyon,  and  Ziphacodon. 

In  our  Western  Miocene,  Carnivores  are  abundant,  and 
make  an  approach  to  modern  types.  The  Felidce,  are  well  rep- 
resented, the  most  interesting  genus  being  Afachairodus,  which 
is  not  uncommon  in  the  Oreodon  beds  on  both  sides  of  the 
Rocky  Mountains.  An  allied  genus  is  Diniclis,  and  several 
smaller  Cats  are  known  from  about  the  same  horizon.  The 
Canidce  are  represented  by  Ampliicyon,  a  European  genus,  and 
by  several  species  of  Cants,  or  a  very  nearly  allied  form.  The 
peculiar  genus  Hycenodon,  found  also  in  Europe,  and  the  type  of 
a  distinct  family,  is  abundant  in  the  Miocene  east  of  the  Rocky 
Mountains,  but  has  not  yet  been  found  on  the  Pacific  Coast. 
In  the  Pliocene  of  both  regions,  the  Canidce  are  numerous, 
and  all  apparently  belong  to  the  existing  genus  Cains.  The 
genus  Machairodus  is  still  the  dominant  form  of  the  Cats,  which 
are  abundant,  and  for  the  most  part  belong  to  the  genus  Felis. 
The  extinct  Leptarctus  is  supposed  to  belong  to  the  Ursidce, 
and  if  so,  is  the  oldest  American  representative  of  this  family. 


46 

In  the  Post-Pliocene,  the  extinct  Felidw  include  species  nearly 
as  large  as  a  lion,  and  smaller  forms  very  similar  to  those  still 
living.  Bears,  Kaccoons  and  Weasels  have  also  been  found. 

In  the  Pliocene  of  South  America,  Machairodus  represents 
the  Felidte,  while  the  genera  Ar cloth erium  and  Hycenarctus 
belong  to  the  Bear  family.  Species  of  Mustela  and  Canis  have 
also  been  found.  In  the  caves  of  Brazil,  the  fauna  of  which 
is  regarded  as  Post-Pliocene,  one  species  of  Machairodus  is 
known,  and  one  of  Syncdurus.  Canis  and  Iclicyon,  still  living 
in  Brazil,  and  the  extinct  genus  Speoihos,  represent  the  Canidce. 
Mephitis  and  Galictis,  among  the  Weasels,  were  also  present, 
and  with  them  species  of  Nasua  and  Arctotheriuin. 

We  come  now  to  the  highest  group  of  Mammals,  the  Pri- 
mates, which  includes  the  Lemurs,  the  Apes,  and  Man.  This 
order  has  a  great  antiquity,  and  even  at  the  base  of  the  Eocene 
we  find  it  represented  by  several  genera  belonging  to  the  lower 
forms  of  the  group.  In  considering  these  interesting  fossils,  it  is 
important  to  have  in  mind  that  the  Lemurs,  which  are  usually 
regarded  as  Primates,  although  at  the  bottom  of  the  scale,  are 
only  found  at  the  present  day  in  Madagascar  and  the  adjacent 
regions  of  the  globe.  All  the  American  Monkeys,  moreover, 
belong  to  one  group,  much  above  the  Lemurs,  while  the  Old 
World  Apes  are  higher  still,  and  most  nearly  approach  Man. 

In  the  lower  Eocene  of  New  Mexico,  we  find  a  few  repre- 
sentatives of  the  earliest  known  Primates,  and  among  them  are 
the  genera  Lemuravus  and  Limnotherium,  each  the  type  of  a 
distinct"  family.  These  genera  became  very  abundant  in  the 
middle  Eocene  of  the  West,  and  with  them  are  found  many 
others,  all  however,  included  in  the  two  families,  Lemuravidce 
and  Limnotheridce.  Lemuravus  appears  to  have  been  most 
nearly  allied  to  the  Lemurs,  and  is  the  most  generalized  form 
of  the  Primates  yet  discovered.  It  had  forty-four  teeth,  form- 
ing a  continuous  series  above  and  below.  The  brain  was 
nearly  smooth,  and  of  moderate  size.  The  skeleton  most 
resembles  that  of  the  Lemurs.  A  nearly  allied  genus,  belong- 
ing to  the  same  family,  is  Hyopsodus.  Limnotherium  (Tomithe- 


47 

ram)  also  is  nearly  related  to  the  Lemurs,  but  shows  some  affin- 
ities with  the  South  American  Marmosets.  This  genus  had 
forty  teeth.  The  brain  was  nearly  smooth,  and  the  cerebellum 
large,  and  placed  mainly  behind  the  cerebrum.  The  orbits  are 
open  behind,  and  the  lachrymal  foramen  is  outside  the  orbit. 
Other  genera  belonging  to  the  Limnotheridce,  are,  Nolharctos, 
Hipposyus,  Microsyops,  Pahmcodon,  TJmwlesles  and  Telmatolestes. 
Besides  these,  Antiacodon  (Anaptomorphus),  Bathrodon  and  Mes- 
acodon  should  probably  be  placed  in  the  same  group.  In  the 
Diplacodon  Beds,  or  Upper  Eocene,  no  remains  of  Primates  have 
yet  been  detected,  although  they  will  doubtless  be  found  there. 
All  the  Eocene  Primates  known  from  American  strata  are  low 
generalized  forms,  with  characters  in  the  teeth,  skeleton  and 
feet  that  suggest  relationships  with  the  Carnivores,  and  even 
with  the  Ungulates.  These  resemblances  have  led  paleontolo- 
gists to  refer  some  imperfect  specimens  to  both  these  orders. 

In  the  Miocene  lake  basins  of  the  West,  only  a  single  spe- 
cies of  the  Primates  has  been  identified  with  certainty.  This 
was  found  in  the  Oreodon  Beds  of  Nebraska,  and  belongs  to 
the  genus  Laopilhecus,  apparently  related  both  to  the  Limno- 
theridce and  to  some  existing  South  American  Monkeys.  In 
the  Pliocene  and  Post-Pliocene  of  North  America,  no  remains 
of  Primates  have  yet  been  found. 

In  the  Post-Pliocene  deposits  of  the  Brazilian  caves,  remains 
of  Monkeys  are  numerous,  and  mainly  belong  to  extinct  spe- 
cies of  Callithrix,  Cebus  and  Jacchus,  all  living  South  American 
genera.  Only  one  extinct  genus,  Protopiihecus,  which  embraced 
animals  of  large  size,  has  been  found  in  this  peculiar  fauna. 

It  is  a  noteworthy  fact,  that  no  traces  of  any  Anthropoid 
Apes,  or  indeed  of  any  Old  World  Monkeys  have  yet  been 
detected  in  America.  Man,  however,  the  highest  of  the  Pri- 
mates, has  left  his  bones  and  his  works  from  the  Arctic  Circle 
to  Patagonia.  Most  of  these  specimens  are  clearly  Post-Ter- 
tiary, although  there  is  considerable  evidence  pointing  to  the 
existence  of  Man  in  our  Pliocene.  All  the  remains  yet  dis- 
covered belong  to  the  well-marked  genus  Homo,  and  apparently 


48 

to  a  single  species,  at  present  represented  by  the  American 
Indian. 

In  tli is  rapid  review  of  Mammalian  life  in  America,  from  its 
first  known  appearance  in  the  Trias  down  to  the  present  time,  I 
have  endeavored  to  state  briefly  the  introduction  and  succes- 
sion of  the  principal  forms  in  each  natural  group.  If  time  per- 
mitted, I  might  attempt  the  more  difficult  task  of  trying  to 
indicate  what  relations  these  various  groups  may  possibly  bear 
to  each  other ;  what  connection  the  ancient  Mammals  of  this 
continent  have  with  the  corresponding  forms  of  the  Old  World; 
and,  most  important  of  all,  what  real  progress  Mammalian  life 
has  here  made  since  the  beginning  of  the  Eocene.  As  it  is,  I 
can  only  say  in  summing  up,  that  the  Marsupials  are  clearly 
the  remnants  of  a  very  ancient  fauna,  which  occupied  this 
continent  millions  of  years  ago,  and  from  which  the  other 
Mammals  were  doubtless  all  derived,  although  the  direct  evi- 
dence of  the  transformation  is  wanting. 

Although  the  Marsupials  are  nearly  related  to  the  still 
lower  Monotremes,  now  living  in  the  Australian  Region,  we 
have  as  yet  no  hint  of  the  path  by  which  these  two  groups 
became  separated  fr.om  the  inferior  vertebrates.  Neither  have 
we  to-day  much  ifght  as  to  the  genetic  connection  existing 
between  Marsupials  and  the  placental  Mammalia,  although  it  is 
possible  that  the  different  orders  of  the  latter  had  their  origin 
each  from  a  separate  group  of  the  Marsupials. 

The  presence,  however,  of  undoubted  Marsupials  in  our 
lower  and  middle  Eocene,  some  of  them  related  to  the  genus 
DidelpJiys,  although  remotely,  is  important  evidence  as  to  the 
introduction  of  these  animals  into  America.  Against  this,  their 
supposed  absence  in  our  Miocene  and  Pliocene  can  have  but 
limited  weight,  when  taken  in  connection  with  the  fact  that 
they  flourished  in  the  Post-Tertiary,  and  are  still  abundant. 
The  evidence  we  now  have  is  quite  as  strongly  in  favor  of  a 
migration  of  Marsupials  from  America  to  the  Old  World,  as  the 
reverse,  which  has  been  supposed  by  some  naturalists.  Possi- 
bly, as  Huxley  has  suggested,  both  countries  were  peopled  with 
these  low  mammals  from  a  continent  now  submerged. 


The  Edentate  mammals  have  long  been  a  puzzle  to  Zoolo- 
gists, and  up  to  the  present  time  no  clew  to  their  affinities  with 
other  groups  seems  to  have  been  detected.  A  comparison  of 
the  peculiar  Eocene  Mammals  which  I  have  called  the  Tillo- 
donlia,  with  the  least  specialized  Edentates,  brings  to  light 
many  curious  resemblances  in  the  skull,  teeth,  skeleton  and 
feet.  These  suggest  relationship,  at  least,  and  possibly  we 
may  yet  find  here  the  key  to  the  Edentate  genealogy.  At 
present,  the  Tillodonts  are  all  from  the  lower  and  middle 
Eocene,  while  Maropus,  the  oldest  edentate  genus,  is  found  in 
the  middle  Miocene,  and  one  species  in  the  lower  Pliocene. 

The  Edentates  have  been  usually  regarded  as  an  American 
type,  but  the  few  living  forms  in  Africa,  and  the  Tertiary 
species  in  Europe,  the  oldest  known,  have  made  the  land 
of  their  nativity  uncertain.  I  have  already  given  you  some 
reasons  for  believing  that  the  Edentates  had  their  first  home 
in  North  America,  and  migrated  thence  to  the  southern 
portion  of  the  continent.  This  movement  could  not  have 
taken  place  in  the  Miocene  period,  as  the  Isthmus  of  Darien 
was  then  submerged ;  but  near  the  close  of  the  Tertiary, 
the  elevation  of  this  region  left  a  much  broader  strip  of  land 
than  now  exists  there,  and  over  this,  the  Edentates  and  other 
mammals  made  their  way,  perhaps  urged  on  by  the  increasing 
cold  of  the  glacial  winters.  The  evidence  to-day  is  strongly  in 
favor  of  such  a  southern  migration.  This,  however,  leaves  the 
Old  World  Edentates,  fossil  and  recent,  unaccounted  for;  but  I 
believe  the  solution  of  this  problem  is  essentially  the  same, 
namely  :  a  migration  from  North  America.  The  Miocene  rep- 
resentatives of  this  group,  which  I  have  recently  obtained  in 
Oregon,  are  older  than  any  known  in  Europe,  and,  strangely 
enough,  are  more  like  the  latter  and  the  existing  African  types 
than  like  any  of  our  living  species.  If,  now,  we  bear  in  mind 
that  an  elevation  of  only  180  feet  would,  as  Dana  has  said, 
close  Behring's  Straits,  and  give  a  road  thirty  miles  wide  from 
America  to  Asia,  we  can  easily  see  how  this  migration  might 
have  taken  place.  That  such  a  Tertiary  bridge  did  exist,  we 
7 


50 

have  much  independent  testimony,  and  the  known   facts  all 
point  to  extensive  migrations  of  animals  over  it. 

The  Cetacea  are  connected  with  the  marine  Carnivores  through 
the  genus  Zeuglodon,  as  Huxley  has  shown,  and  the  points  of 
resemblance  are  so  marked  that  the  affinity  cannot  be  doubted. 
That  the  connection  was  a  direct  one,  however,  is  hardly  prob- 
able, since  the  diminutive  brain,  large  number  of  simple  teeth, 
and  reduced  limbs  in  the  Whales,  all  indicate  them  to  be  an- 
old  type,  which  doubtless  branched  off  from  the  more  primi- 
tive stock  leading  to  the  Carnivores.  Our  American  extinct 
Cetaceans,  when  carefully  investigated,  promise  to  throw  much 
light  upon  the  pedigree  of  these  strange  mammals.  As  most 
of  the  known  forms  were  probably  marine,  their  distribution  is 
of  little  service  in  determining  their  origin. 

That  the  Sirenians  are  allied  to  the  Ungulates,  is  now  gen- 
erally admitted  by  anatomists,  and  the  separation  of  the  exist- 
ing species  in  distant  localities  suggests  that  they  are  the  rem- 
nants of  an  extensive  group,  once  widely  distributed.  The 
large  number  of  teeth  in  some  forms,  the  reduced  limbs  and 
other  characters,  point  back  to  an  ancestry  near  that  of  the 
earliest  ungulates.  The  gradual  loss  of  teeth  in  the  specialized 
members  of  this  group,  and  in  the  Cetaceans,  is  quite  parallel 
with  the  same  change  in  Edentates,  as  well  as  in  Pterodactyls 
and  Birds. 

The  Ungulates  are  so  distinct  from  other  groups  that  they 
must  be  one  of  the  oldest  natural  divisions  of  mammals,  and 
they  probably  originated  from  some  herbivorous  marsupial. 
Their  large  size,  and  great  numbers  during  Tertiary  and  Post- 
tertiary  time,  render  them  most  valuable  in  tracing  migrations 
induced  by  climate,  as  well  as  in  showing  the  changes  of 
structure  which  such  a  contest  for  existence  may  produce. 

In  the  review  of  the  extinct  Ungulates,  I  have  endeavored 
to  show  that  quite  a  number  of  genera  usually  supposed  to 
belong  originally  to  the  Old  World  are  in  reality  true  Amer- 
ican types.  Among  these  were  the  Horse,  Rhinoceros,  and 
Tapir,  all  ,the  existing  odd-toed  Ungulates,  and  besides  these 


51 

the  Camel,  Pig,  and  Deer.  All  these  I  believe,  and  many 
others,  went  to  Asia  from  our  North  West  Coast.  It  must,  for 
the  present,  remain  an  open  question  whether  we  may  not 
fairly  claim  the  Bovidce,  and  even  the  Proboscidea,  since  both 
occur  in  our  strata  at  about  the  same  horizon  as  on  the  other 
continent.  On  this  point  there  is  some  confusion,  at  least  in 
names.  The  Himalayan  deposits  called  Upper  Miocene,  and 
so  rich  in  Proboscideans,  indicate  in  their  entire  fauna  that 
they  are  more  recent  than  our  Niobrara  River  beds,  which,  for 
apparently  good  reasons,  we  regard  as  Lower  Pliocene.  The 
latter  appear  to  be  about  the  same  horizon  as  the  Pikermi 
deposits  in  Greece,  also  regarded  as  Miocene.  Believing,  how- 
ever, that  we  have  here  a  more  complete  Tertiary  series,  and  a 
better  standard  for  comparison  of  faunas,  I  have  preferred  to 
retain  the  names  already  applied  to  our  divisions,  until  the 
strata  of  the  two  continents  are  more  satisfactorily  coordinated. 

The  extinct  Eodents,  Bats,  and  Insect! vores  of  America, 
although  offering  many  suggestive  hints  as  to  their  relation- 
ship with  other  groups,  and  their  various  migrations,  cannot 
now  be  fully  discussed.  There  is  little  doubt,  however,  that 
the  Rodents  are  a  New  World  type,  and,  according  to  present 
evidence,  they  probably  had  their  origin  in  North  America. 
The  resemblance  in  so  many  respects  of  this  order  to  the 
Proboscideans  is  a  striking  fact,  not  yet  explained  by  the  im- 
perfectly known  genealogy  of  either  group. 

The  Carnivores,  too,  I  must  pass  by,  except  to  call  attention 
to  a  few  special  forms  which  accompanied  the  migrations  of 
other  groups.  One  of  these  is  Maclmirodus,  the  saber-toothed 
Tiger,  which  flourished  in  our  Miocene  and  Pliocene,  and 
followed  the  huge  Edentates  to  South  America,  and  the  Ungu- 
lates across  Asia  to  Europe.  With  this  genus  went  Hycenodon, 
and  some  typical  Wolves  and  Cats,  but  the  Bears  came  the 
other  way  with  the  Antelopes.  That  the  Gazelle,  Giraffe,  Hip- 
popotamus, Hyaena  and  other  African  types,  once  abundant  in 
Asia,  did  not  come,  is  doubtless  because  the  Miocene  bridge 
was  submerged  before  they  reached  it. 


52 

The  Edentates,  in  their  southern  migration,  were  probably 
accompanied  by  the  Horse,  Tapir  and  Rhinoceros,  although  no 
remains  of  the  last  have  yet  been  found  south  of  Mexico.  The 
Mastodon,  Elephant,  Llama,  Deer,  Peccary,  and  other  mam- 
mals, followed  the  same  path.  Why  the  Mastodon,  Elephant, 
Ehinoceros,  and  especially  the  Horse,  should  have  been  selected 
with  the  huge  Edentates  for  extinction,  and  the  other  Un- 
gulates left,  is  at  present  a  mystery,  which  their  somewhat 
larger  size  hardly  explains. 

The  relations  of  the  American  Primates,  extinct  and  recent, 
to  those  of  the  other  hemisphere,  offer  an  inviting  topic,  but  it 
is  not  in  my  present  province  to  discuss  them  in  their  most 
suggestive  phases.  As  we  have  here  the  oldest  and  most 
generalized  members  of  the  group,  so  far  as  now  known,  we 
may  justly  claim  America  for  the  birth-place  of  the  order. 
That  the  development  did  not  continue  here  until  it  culmi- 
nated in  Man,  was  due  to  causes  which  at  present  we  can  only 
surmise,  although  the  genealogy  of  other. surviving  groups 
gives  some  data  towards  a  solution.  Why  the  old  world  Apes, 
when  differentiated,  did  not  come  to  the  land  of  their  earlier 
ancestry,  is  readily  explained  by  the  then  intervening  oceans, 
which  likewise  were  a  barrier  to  the  return  of  the  Horse  and 
Rhinoceros. 

Man,  however,  came ;  doubtless  first  across  Behring's 
Straits ;  and  at  his  advent  became  part  of  our  fauna,  as  a 
mammal  and  primate.  In  these  relations  alone,  it  is  my  pur- 
pose here  to  treat  him.  The  evidence,  as  it  stands  to-day, 
although  not  conclusive,  seems  to  place  the  first  appearance  of 
Man  in  this  country  in  the  Pliocene,  and  the  best  proof  of 
this  has  been  found  on  the  Pacific  coast.  During  several 
visits  to  that  region,  many  facts  were  brought  to  my  knowl- 
edge which  render  this  more  than  probable.  Man  at  this  time 
was  a  savage,  and  was  doubtless  forced  by  the  great  volcanic 
outbreaks  to  continue  his  migration.  This  was  at  first  to  the 
south,  since  mountain  chains  were  barriers  on  the  east.  As 
the  native  Horses  of  America  were  now  all  extinct,  and  as  the 


53 

early  man  did  not  bring  the  old  world  animal  with  him,  his 
migrations  were  slow.  I  believe,  moreover,  that  his  slow  pro- 
gress towards  civilization  was  in  no  small  degree  due  to  this 
same  cause,  the  absence  of  the  Horse. 

It  is  far  from  my  intention  to  add  to  the  many  theories  ex- 
tant in  regard  to  the  early  civilizations  in  this  country,  and 
their  connections  with  the  primitive  inhabitants,  or  the  later 
Indians,  but  two  or  three  facts  have  recently  come  to  my 
knowledge  which  I  think  worth  mentioning  in  this  connection. 
On  the  Columbia  River,  I  have  found  evidence  of  the  former 
existence  of  inhabitants  much  superior  to  the  Indians  at  pres- 
ent there,  and  of  which  no  tradition  remains.  Among  many 
stone  carvings  which  I  saw  there,  were  a  number  of  heads 
which  so  strongly  resemble  those  of  Apes,  that  the  likeness  at 
once  suggests  itself.  Whence  came  these  sculptures,  and  by 
whom  were  they  made?  Another  fact  that  has  interested  me 
very  much  is  the  strong  resemblance  between  the  skulls  of  the 
typical  Mound-builders  of  the  Mississippi  Valley  and  those  of 
the  Pueblo  Indians.  I  had  long  been  familiar  with  the  former, 
and  when  I  recently  saw  the  latter,  it  required  the  positive 
assurance  of  a  friend  who  had  himself  collected  them  in  New 
Mexico,  to  convince  me  that  they  were  not  from  the  mounds. 
A  third  fact,  and  I  leave  Man  to  the  Archaeologists,  on  whose 
province  I  am  even  now  trenching.  In  a  large  collection  of 
Mound-builders'  pottery,  over  a  thousand  specimens,  which 
I  have  recently  examined  with  some  care,  I  found  many 
pieces  of  elaborate  workmanship  so  nearly  like  the  ancient 
water-jars  from  Peru,  that  no  one  could  fairly  doubt  that  some 
intercourse  had  taken  place  between  the  widely  separated  peo- 
ple that  made  them. 

The  oldest  known  remains  of  Man  on  this  continent  differ 
in  no  important  characters  from  the  bones  of  the  typical 
Indian,  although  in  some  minor  details  they  indicate  a  much 
more  primitive  race.  These  early  remains,  some  of  which  are 
true  fossils,  resemble  much  more  closely  the  corresponding 
parts  of  the  highest  Old  World  Apes,  than  do  the  latter  our 


54 

Tertiary  Primates,  or  even  the  recent  American  Monkeys. 
Various  living  and  fossil  forms  of  old  world  Primates  fill  up 
essentially  the  latter  gap.  The  lesser  gap  between  the  prim- 
itive Man  of  America  and  the  Anthropoid  Apes  is  partially 
closed  by  still  lower  forms  of  men,  and  doubtless  also  by  higher 
Apes,  now  extinct.  Analogy,  and  many  facts  as  well,  indicate 
that  this  gap  was  smaller  in  the  past.  It  certainly  is  becoming 
wider  now  with  every  generation,  for  the  lowest  races  of  men 
will  soon  become  extinct,  like  the  Tasmanians,  and  the  highest 
Apes  cannot  long  survive.  Hence  the  intermediate  forms  of 
the  past,  if  any  there  were,  become  of  still  greater  importance. 
For  such  missing  links,  we  must  look  to  the  caves  and  later 
Tertiary  of  Africa,  which  I  regard  as  now  the  most  promising 
field  for  exploration  in  the  Old  World.  America,  even  in  the 
Tropics,  can  promise  no  such  inducements  to  ambitious  ex- 
plorers. We  have,  however,  an  equally  important  field,  if 
less  attractive,  in  the  Cretaceous  Mammals,  which  must  have 
left  their  remains  somewhere  on  this  continent.  In  these  two 
directions,  as  I  believe,  lie  the  most  important  future  discov- 
eries in  Paleontology. 

As  a  cause  for  many  changes  of  structure  in  mammals 
during  the  Tertiary  and  Post-Tertiary,  I  regard,  as  the  most 
potent,  Natural  Selection,  in  the  broad  sense  in  which  that  term 
is  now  used  by  American  evolutionists.  Under  this  head,  I 
include  not  merely  a  Malthusian  struggle  for  life  among  the 
animals  themselves,  but  the  equally  important  contest  with  the 
elements,  and  all  surrounding  nature.  By  changes  in  the  envi- 
ronment, migrations  are  enforced,  slowly  in  some  cases,  rapidly 
in  others,  and  with  change  of  locality  must  come  adaptation  to 
new  conditions,  or  extinction.  The  life-history  of  Tertiary 
mammals  illustrates  this  principle  at  every  stage,  and  no  other 
explanation  meets  the  facts. 

The  real  progress  of  mammalian  life  in  America,  from  the 
beginning  of  the  Tertiary  to  the  present,  is  well  illustrated  by 
the  Brain-growth,  in  which  we  have  the  key  to  many  other 
changes.  /The  earliest  known  Tertiary  mammals  all  had  very 


55 

small  brains,  and  in  some  forms  this  organ  was  proportionally 
less  than  in  certain  Reptiles.  There  was  a  gradual  increase  in 
the  size  of  the  brain  during  this  period,  and  it  is  interesting  to 
find  that  this  growth  was  mainly  confined  to  the  cerebral 
hemispheres,  or  higher  portion  of  the  brain.  In  most  groups 
of  mammals,  the  brain  has  gradually  become  more  convoluted, 
and  thus  increased  in  quality,  as  well  as  quantity.  In  some, 
also,  the  cerebellum,  and  olfactory  lobes,  the  lower  parts  of  the 
brain,  have  even  diminished  in  size.  In  the  long  struggle  for 
existence  during  Tertiary  time,  the  big  brains  won,  then  as 
now ;  and  the  increasing  power  thus  gained  rendered  useless 
many  structures  inherited  from  primitive  ancestors,  but  no 
longer  adapted  to  new  conditions. 

Another  of  the  interesting  changes  in  mammals  during  Ter- 
tiary time  was  in  the  teeth,  which  were  gradually  modified 
with  other  parts  of  the  structure.  The  primitive  form  of  tooth 
was  clearly  a  cone,  and  all  others  are  derived  from  this.  All 
classes  of  vertebrates  below  mammals,  namely,  Fishes,  Amphi- 
bians, Reptiles,  and  Birds,  have  conical  teeth,  if  any,  or  some 
simple  modification  of  this  form.  The  Edentates  and  Ceta- 
ceans with  teeth  retain  this  type,  except  the  Zeuglodonts,  which 
approach  the  dentition  of  aquatic  Carnivores.  In  the  higher 
mammals,  the  incisors  and  canines  retain  the  conical  shape,  and 
the  premolars  have  only  in  part  been  transformed.  The  latter 
gradually  change  to  the  more  complicated  molar  pattern,  and 
hence  are  not  reduced  molars,  bat  transition  forms  from 
the  cone  to  more  complex  types.  Most  of  the  early  Tertiary 
mammals  had  forty-four  teeth,  and  in  the  oldest  forms  the 
premolars  were  all  unlike  the  molars ;  while  the  crowns  were 
short,  covered  with  enamel,  and  without  cement.  Each  stage 
of  progress  in  the  differentiation  of  the  animal  was,  as  a  rule, 
marked  by  a  change  in  the  teeth ;  one  of  the  most  common 
being  the  transfer,  in  form  at  least,  of  a  premolar  to  the  molar 
series,  and  a  gradual  lengthening  of  the  crown.  Hence,  it  is 
often  easy  to  decide  from  a  fragment  of  a  jaw,  to  what  horizon 
of  the  Tertiary  it  belongs.  The  fossil  Horses  of  this  period, 


56 

for  example,  gained  a  grinding  tooth,  for  each  toe  they  lost, 
one  in  each  epoch.  In  the  single-toed  existing  horses,  all  the 
premolars  are  like  the  molars,  arid  the  process  is  at  an  end. 
Other  dental  transformations  are  of  equal  interest,  but  this 
illustration  must  suffice. 

The  changes  in  the  limbs  and  feet  of  mammals  during  the 
same  period  were  quite  as  marked.  The  foot  of  the  primitive 
mammal  was  doubtless  plantigrade,  and  certainly  five-toed. 
Many  of  the  early  Tertiary  forms  show  this  feature,  which  is 
still  seen  in  some  existing  forms.  This  generalized  foot  became 
modified  by  a  gradual  loss  of  the  outer  toes,  and  increase  in 
size  of  the  central  ones ;  the  reduction  proceeding  according  to 
systematic  methods,  differing  in  each  group.  Corresponding 
changes  took  place  in  the  limb  bones.  One  result  was  a  great 
increase  in  speed,  as  the  power  was  applied  so  as  to  act 
only  in  the  plane  of  motion.  The  best  effect  of  this  speciali- 
zation is  seen  to-day  in  the  Horse  and  Antelope,  each  repre- 
senting a  distinct  group  of  Ungulates,  with  five-toed  ancestors. 

If  the  history  of  American  Mammals  as  I  have  briefly 
sketched  it,  seems  as  a  whole  incomplete,  and  unsatisfactory, 
we  must  remember  that  the  genealogical  tree  of  this  class  has  its 
trunk  and  larger  limbs  concealed  beneath  the  debris  of  Meso- 
zoic  time,  while  its  roots  doubtless  strike  so  deeply  into  the 
Paleozoic  that  for  the  present  they  are  lost.  A  decade  or  two 
hence,  we  shall  probably  know  something  of  the  mammalian 
fauna  of  the  Cretaceous,  and  the  earlier  lineage  of  our  existing 
mammals  can  then  be  traced  with  more  certainty. 

The  results  I  have  presented  to  you  are  mainly  derived 
from  personal  observation  ;  and  since  a  large  part  of  the  higher 
vertebrate  remains  found  in  this  country  have  passed  through 
my  hands,  I  am  willing  to  assume  full  responsibility  for  my 
presentation  of  the  subject. 

For  our  present  knowledge  of  the  .extinct  Mammals,  Birds 
and  Reptiles  of  North  America,  science  is  especially  indebted 
to  Leidy,  whose  careful,  conscientious  work  has  laid  a  secure 


57 

foundation  for  our  vertebrate  palaeontology.  The  energy  of 
Cope  has  brought  to  notice  many  strange  forms,  and  greatly 
enlarged  our  literature.  Agassiz,  Owen,  Wyman,  Baird, 
Hitchcock,  Deane,  Emmons,  Lea,  Allen,  Gibbes,  Jefferson, 
DeKay,  and  Harlan,  deserve  honorable  mention  in  the  history 
of  this  branch  of  science.  The  South  American  extinct  verte- 
brates have  been  described  by  Lund,  Owen,  Burmeister,  Ger- 
vais,  Huxley,  Flower,  Desmarest,  Aymard,  Pictet,  and  Nodot. 
Darwin  and  Wallace  have  likewise  contributed  valuable  infor- 
mation on  this  subject,  as  they  have  on  nearly  all  forms  of  life. 

In  this  long  history  of  ancient  life  I  have  said  nothing  of 
what  Life  itself  really  is.  And  for  the  best  of  reasons,  because 
I  know  nothing.  Here  at  present  our  ignorance  is  dense,  and 
yet  we  need  not  despair.  Light,  Heat,  Electricity,  and  Magnet- 
ism, Chemical  Affinity  and  Motion,  are  now  considered  different 
forms  of  .the  same  force;  and  the  opinion  is  rapidly  gaining 
ground  that  Life,  or  vital  force,  is  only  another  phase  of  the 
same  power.  Possibly  the  great  mystery  of  Life  may  thus  be 
solved,  but  whether  it  be  or  not,  a  true  faith  in  Science  knows 
no  limit  to  its  search  for  Truth. 


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